In a situation like that, Screen Time (built-in feature) may give you some hints; explore it to see what sort of information is available. Based on that info, since Screen Time gives a daily/hourly breakdown of app usage, you could conjecture what apps were used for how long at which times, although all this info usually can’t be determined precisely.

Replace the battery or pay to have it replaced.

iFixit sells good quality aftermarket batteries if you want to do it yourself (which I do recommend)

It’s impossible

I just didn’t get used to it, lol. Switched from iPhone 7 to 12 pro to se2 back to the same 12 pro and then to se3. The gestures all became muscle memory but having a notch and face ID instead of touch ID still sucked