Part of screen not working, same with lock button! Help!

I think you need a new screen. The repair guide lists the job as Difficult and there’s a lot of disassembly to do, but don’t be put off. So long as you’re well organised, make sure you note which particular screws came out in which steps so you can put them back correctly, and you have a fair bit of patience, it isn’t that hard. You just have to be very careful feeding the LCD and touchscreen cables through a slot in the midframe as there is a weak point on the inside of a bend in the ribbon where they can very easily tear. Having removed the old screen, practice reinstalling and removing it until you’ve mastered it before risking the new screen.

Or, you can take it into a shop - at that age the screen won’t be too expensive and it’ll be a fairly standard job for an experienced repair technician.