It is better to do a factory reset after battery replacement. The ‘software’ perhaps is still using ‘calibration’ from old battery. Just copy all your files and reset!
Which model? See this: Acer Chromebook C720 Solid State Drive (SSD) Replacement Google/look in youtube - most likely it is a loose contact that SDD is disconnected. Gently unscrew - check everything like loose cables/connections. Try. alternately, the SSD is damaged. Buy an replacement. See Acer Chromebook C720 Solid State Drive (SSD) Replacement Post here again…
"I think this whole situation all started when I first opened the back of the phone and put it back. Please help me with how to fix it and what not to do with the phone." Electronics are very fragile. Just be careful - but good news - u became a good hobbiyist and reparier - learn by reading the different teardowns in ifixit - be gentle when opening phone SMACKING is not to do!!! "I smacked it on my lap to work and it did."
May be download ‘app’ to power off phone. But be careful - if your power button is defective - you cannot switch it on. Or do u mean Display? Settings -> Display -> Change timeout
I changed Step 8: Typo: principle to principal. Sorry!