PROBLEM SOLVED, Don't know how or why - as follows.
It is now 9 hours later and I have edited a handful of notes from my Win10 PC EN on Chrome Browser. I opened a few existing notes individually, and added a "space". I did this via the EN Web front end. I then opened the EN iOS app 10.1 (which I had updated yesterday), and voila, I could EDIT not only the ones that I updated from my PC, but all other notes (as far as I can see so far). The green VIEW ONLY icon on all (I hope) my notes is now a BLUE EDIT icon. YAY!!!
I had previously tried the SYNC NOW function from my phone but that did not make any difference even when the message was SYNC COMPLETE.
I did not do anything else to the iOS app. I am rather confused but very happy that the iOS app is working per normal (with new GUI).
Thank you everyone who offered suggestions. I apologise in advance that I am no more enlightened as to what caused the EDIT/VIEW ONLY issue that I outlined above, and how to fix it. Maybe @PinkElephant is correct, it is patience that is required. But goodness! Lucky for me, iOS EN is important for me but not critical. I feel sorry for those who are much more dependent on iOS EN.
(I failed to mention that I normally use the EN web GUI from a Chrome Browser on my Win10 PC. I only use the Win10PC desktop client for making version backups of my notes.)