I have been using my MacBook Air since 8 years, it has been having an issue with its keyboard and trackpad at the point...

You have to contact the previous owner, tell them to remove the Apple Watch from their iCloud account. That is the only solution or the device is basically unusable

All MacBook Pros from 2016 to 2019 suffer from a flex cable issue called "flexgate". This means that the cable that connects the display to the main logicboard is too small and hence, it tears a bit when you open the lid too much, Apple has launched a replacement program for the users to give a free replacement of the faulty display. So you need to take it to an Apple Store and get them to replace the screen. Hope this answer helped :D

If this reboots on its own, then it can be a battery problem. If you can, get a technician to diagnose the problem and replace the battery

I have a Note10+ too, its in fine condition, what your issue seems to be is the adhesive is becoming loose, have you repaired your device at any point?