Re: If you've tried everything and it still doesn't work
Firstly, it appears we are the unfortunate segment. I've been warning all my iphone users not to upgrade but it appears many have already upgraded but don't experience this freeze problem.
Thanks for all the brilliant suggestions. I tried the various ideas ...
1. @ToxRowlang's idea to Reset Location settings back to original. It worked for 3 hours, then slowly degraded over 24-48 hours back to horrible freeze.
2. Later I tried @JesperDenmark idea which is to delete Tinder. I don't have Tinder - but I deleted all third party apps (anything that Apple did not provide as part of basic phone) - and reinstalled only if needed. Phone is 50% better but still occasionally lagging and freezing but at least not indefinitely or not as frequent.
3. I had enough and tried to downgrade to 10.3.3. At first I hit error 4000 (so I updated iTunes, turn off firewall & virus protect). Then I hit error 3194 (which means Apple doesn't allow downgrade ie 10.3.3 is no longer signed off the firmware).
4. I have tried @tushar_mehta's ideas of messing with selected Settings but didn't really help.
My current conclusion and options:
a) Wait for Apple to really fix it with a working iOS
b) when I have time, I'll hack away error 3194 to downgrade to 10.3.3 and stay there.
c) change phone to X, or more likely Samsung S8 or Note 8. I like Apple a lot & I understand technical blunders happen but this lack of accountability (quiet, no acknowledgement, etc) from them really frustrates me.
Will also keep trying your hacks guys. Thx.