PinkElephant

Log out, close the client, uninstall, if asked dump all data.
Make a forced restart of the iPhone, reinstall, open, log in.
The only thing you loose  temporarily are notes downloaded for offline use. But they will be recovered from the server after reinstalling, if you want the download.

Then your local PC database has taken a hit. 
To fix it do this:
Confirm there are no notes that are on the PC, but NOT on the web. Export them, or they get lost.
Log out on PC, quit the client. Now use Revo Uninstaller (free on the web) to purge all parts of the existing EN install. Restart the PC.
Get the new client from the EN website. Install, log in. Your notes should now sync from the server.
Let the client run in the background for an extended period of time. It will download the full data from the server.

AFAIK it's page numbers, with some formatting options.
BTW exporting to pdf is not really a good idea if you want to save your notes somehow. Attachments will be lost (except pictures).

Sure, go to iOS settings, display and brightness. Reduce the standard text size, which in your case is probably set to pretty large.
This makes the close - X visible.

@featherhead@mac.com on the Mac all menus are always at the top of the screen, not on top of the application window.
To see the editing options in the note you first need to place the cursor in it. Then they show.

Follow the link I have posted.
If you have lost access to the email address it’s THE ONLY WAY to gain back access.
We are other users here and can’t help you any further.

Maybe you have a bunch of leftovers from an older install.
Beside this ENEX files never get removed.In your case most are not files, but shortcuts pointing at files. Probably the files were removed, leaving orphaned shortcuts behind.

Minimum system requirement for iOS is iOS 13.
You‘re out of luck.

The first question for me is what is a sensitive document. Tax return ? I wouldn‘t publish it, but sensitive ? Personal documents ? The same. Medical records - maybe, depending on the content. Business proceeds ? I am working as a Freelancer, and EN is my business driver. For sure there is business related information there, I couldn‘t work otherwise. So I have a Data Processing Agreement with EN, which is a legal requirement under GDRP. I think most of the data in a typical EN account is really sensitive, in the meaning of critically damaging if discovered.
The main issue is to keep account access secure: Long password plus 2 FA enabled.
Who wants more secure storage can store a encrypted container in a note, export it, open it, store whatever into it, close and encrypt it and store it back. It is a PITA, but really not much different to using such containers in another cloud service.
Given the situation with access by authorities to cloud storages, I would never entrust ANY service with storing confidential information that is holding the keys to it as well. It‘s the same reason why I don‘t store passwords AND the 2FA-keys in the same password manager.
In the end only a cold storage or wallet is really keeping your data completely safe - just don‘t loose it, or forget the keys.

Full uninstall, using AppCleaner. Download fresh installer from the EN website, not the AppStore.
After open and login, let it run for quite a while. It will download a fresh copy of your database.
The reason for slugginess is in most cases a damaged local database, that needs to be replaced.

There is a more than simple explanation: You can’t share notebooks by public link any more.
This was removed 3 years ago - maybe some older links continued to work.
Notebooks can only be shared to defined, known recipients now.
If you want to publicly share, take a look at postach.io 

Then probably your local database is corrupted.
Uninstall the client using AppCleaner. The Mac uninstaller won't do.
After that, download a fresh copy from the EN website, install and log in. Should work now.
Let the client run in the background, it will take time to download everything.

Open the tags view, swipe the tag to the left: A 3 dot button appears.
Tap on it, and all options are available from a popup menu.

Personally I would try to contact support. Ticket type Account and Payment&Billing is open for all users:
https://help.evernote.com/hc/en-us/requests/new Or use the support access as a guest:
https://help.evernote.com/hc/en-us/requests/new?ticket_form_id=254668&guest=true&guest=true

No, they won’t. But you can’t add more, and you can’t reorganize your notebooks.
The new Free is a trial, and you are beyond that. Decide to pay, or leave exporting your stuff.

You have chosen a large setting for the system text style.
Open iOS settings, display & brightness and scale down the standard text size. Then you can confirm the initial screen, and go on with using the app.

It could be done this way, but first read it all:
Export the notes from the notebooks you want to remove to ENEX files.
Scrap the notebooks, empty the trash - on deleting a notebook, the notes end up in trash.
When you are down to 1 notebook, import the ENEX files.
But beware: You only have an upload limit of 60MB every 30 days. So depending on note sizes, you can get beyond it pretty fast.
And then it wouldn’t import at all !
So maybe subscribe for a month, and then you could move everything directly as well.

There is no difference between the plans called the same.
AFAIK this is the only way the AppStore can display prices when different groups of users are eligible for different prices (like rebated vs. regular).
When you try a subscription where you are not eligible, you can’t continue the process.
Not really good, but that’s an AppStore thing EN can hardly change.

The link to support is in all clients, and in all help articles in the help database. But since this obviously not enough, here is a direct link to open a ticket:
Evernote Support Ticket:   https://help.evernote.com/hc/en-us/requests/new

You want to pass on the content ?
Export as HTML, save it to a drive / USB stick or online cloud, hand it over. The content can be accessed with every browser. The attachments are there, in a folder inside of the export.
Exporting as pdf doesn't take the attachments along. Export as ENEX needs an import (like into EN or another notes app) to be readable.
You could share the notes as well, but this means you need to keep your account alive to keep the share working.

To contact EN officially, try this:
https://help.evernote.com/hc/en-us/requests/new Or use the feedback function build into the clients.
As a longterm user you probably have noticed that while all cost were going up, EN had maintained a flat price level for years. Part of the raise we see now is just making up for missed increases in the past. Another part is probably due to the fact that under the former owners, the company was not profitable in years. If you are interested in a sustained operation of EN, you surely understand why it is necessary they refinance themselves from their subscription income. Since EN does not trade with it's users data, the subscriptions are the principal source of revenue.

No, legacy apps will not sync any more. Maybe 7.14 will sync, no idea. But if it does, it will stop any time now as well.
You can access your notes through other clients, like the web client.
Your version of MacOS can’t run the current v10 client. You need at least MacOS 10.14 Mojave. 
So either you update it, or it’s the end of the road for the desktop client for you.

Very simple: What you created is a checklist, not a checkbox. A checklist is a formatting for lists. It’s meant for several rows of text, with a tickable box at the beginning of each row. If selected it can create a strikeout of the text when ticked.
A checkbox is a special text character in the form of a box, that can be ticked off. It should be used somewhere in between other text, never at the beginning of a line.
Advise: Never try to use checkboxes to build a checklist.

Can’t reproduce this for dates. To prevent numbers to convert into phone numbers, the setting is in app settings, notes, advanced editing.

You check it word by word yourself.
There is no tool to compare versions.
Or you copy the text to an app that supports comparing 2 documents, and use it to find the difference. MS Word comes to mind, or if you want a free alternative LibreOffice.