Unfortunately, 5 to 10 seconds of time spent in water is more than enough time to fry the motherboard. Although this may not be true to your device specifically, water damaged devices (even after attempted repairs) are very unreliable. They can work for 5 minutes, 5 days, or 5 weeks, but if it breaks again you’re out of luck. If there is personal data that you would like to retrieve, try sending it to a data recovery company such as “Drive Savers”. If you would still like to try and get it fixed, I personally don’t know of any companies that I could recommend. I hoped this helped!
This may be a long shot but I would try removing the cmos battery and letting the laptop sit for ~30 seconds, then put it back in. If that doesn’t work, try re-seating ram sticks one by one to see if one is at fault.
Seems like a battery issue. The battery performance has decreased, due to its age, so much it cant even boot the phone. A good battery for a iPhone 4 is roughly $15-$30 As for the screen getting darker. That can be a multitude of things. The most common thing i have found to cause that is either the battery or a bad screen.
Personally I would get the new version controller from a Microsoft store, not online. Or bring it into a store and see what they can do about it. It might be just a coincidence that both controllers are bad.
A back glass repair is virtually impossible without breaking any internal parts. Apple doesn’t sell their OEM parts like Samsung does. I would bite the bullet and get a case that covers the cracks or spend Apples premium to get it fixed.