depending on your phone Rice may not actually do anything at all. phones these days are compact tightly designed machines and for rice to work it has to come into contact with the water more or less. the water isn’t able to escape towards the rice so it stays in the device. first step is to remove the battery and clean the motherboard. isopropyl alcohol should be enough if not much corrosion has occurred. when that’s done based on your description you most likely need to replace the screen assembly. of course it’s also possible the water did permanent damage to the display circuit which would require a specialist to fix. if you give us the model # of your phone it could help us help you as well
Open it up and feel the adhesive. The stock would have to be pretty old for the adhesive to not stick. Also make sure the chassis is completely cleaned of dust and old adhesive from the previous battery. Dirty chassis will make new adhesive not sticky. Worst case you can buy some double sided adhesive, I’d recommend red tape for it, and re-adhere battery to the chassis if the above doesn’t help.
you said the original mac was badly bent, was the motherboard badly bent as well? it’s possible for mobo to have been bent and cracked internally and have still been working as the bend could have also been forcing the inner connection lines together and when removed that force was no longer applied and they separated. Louis Rossman has a lot of great videos on diagnosing charging on these devices on the mobo so could definitley be worth looking at. I will say that only 1 USB port charging device also kinda lends itself to saying mobo has damage I think. Also the 1% battery on apple devices tends to be damaged mobo components (on iphones for example, usually a capacitor next to the battery terminal). If your battery has its own daughterboard it could be battery as well. also the new battery could be bad. never a guarantee with it, you can always transfer your mobo back to the old case loosely just enough to turn on with the battery and see if it turns on. if it does then the new battery may just be bad....
if you have a spare keyboard lying around, a USB one, plug it in and see if it works. if it works fine then it’s probably just your replacement keyboard. if it doesn’t then it’s probably an issue with software on the device itself. that’s a fairly universal way to tell if a keyboard on laptop is bad. that said it does just sound like a bad keyboard replacement since the old one was working until alcohol got on it. you could also try the original after letting it dry for a few days as if you were using 99% isopropyl alcohol it would probably just need dried out first.
you said heat sink doesn’t get super hot. this is bad. the heat sink is supposed to be very hot because that means it’s doing its job, that it is transferring heat away from the main processor. you said you cleaned out dust, did you re thermal the processor? especially if you removed the heat sink, it will need new thermal paste. if it still shuts down randomly at that point it is most likely either HDD or Mobo issue
crashing in PS4 is due to one of 2 things from my experience. Overheating, or HDD failure. First step, clean dust out of device and apply new thermal paste. If device still crashes, and you have a good HDD laying around, try and install it in device and see if it fixes it. Also make sure you have games backed up as once you do a reinstall they’ll be lost from HDD Edit: also, I’m unsure of repair shops in Germany, but many over here in the US including the one I work at work on a no fix no charge process. You may have to look around, or maybe there’s one you would be able to ship the device off to for a reasonable shipping cost.
unless the snapped disc damaged the drive, the shop is just trying to get you on a replacement. it is 100% possible to remove the disc drive and take the drive itself apart to remove the disc. I’d find another shop that is more helpful and willing to work with you on it, removing the disc and charging you a labor fee if the drive still works and if it doesn’t then offer you a replacement cost. you could also try it yourself, but there are dangers involved for an expensive machine like this. I believe there’s an ifixit guide on removing the disc drive however
as chris said back camera can cause front to not work as well. try disconnecting the back camera and see if the front camera works (may or may not). also, what repair did you do? I’m assuming a screen replacement (most common repair on a phone after all). Check to make sure the prox/front camera flex cable didn’t receive any damage as well. Clean connectors for both front and back cameras. Power cycle device (disconnect battery and hold power button for 10-15 seconds to flush all power out of the board). If nothing else you can try to do a factory restore via itunes and see if there is a software glitch that caused the issue. That’s about all I can think of that may help restore functionality though beyond replacing the (most likely just the) rear camera, which for some reason is more expensive on the iphone 7 plus than any other iphone I’ve seen including xs max.
you may be able to splice the existing cable to a replacement. however the replacement would most likely need to be an OEM one from another broken device or such, and would require microsoldering equipment/experience. a replacement home button may not have touch id but it’ll still work fine as a home button