Well sadly, your phone won't turn on anymore. Once the components get wet, they won't work again. Rice won't solve this, replacing the components can but that'll cost you more than the iPhone 7 is worth. If you have warranty, try to get a new one, if not I don't know, I'm sorry.

Well, I can tell you this. the beeps are supposed to indicate errors (RAM Failure, Boot Drive not found, etc). You already concluded it's not the RAM, Harddrive, Motherboard, PSU or I/O ports. But it seems the only logical option would be the screen itself not working. Try replugging the screen of the computer itself if that's possible. Otherwise try to take it to a repair shop and they can most likely fix it.

Well I wouldn't suggest replacing the logicboard unless you can confirm all components are compatible. And your phone in theory should be able to handle 64GB, So short answer, yes you can IF the 64GB chip is not a separate component from the logicboard.

I say don't worry. Others might disagree I know on iPhones the Fingerprint sensor is directly above the charging port so the charging port is overheating, In your case (I don't know where the sensor is to be fair), try rebooting it, and see if no other component is causing the overheating. If it gets worse over time, replace the component that causes the overheating, or take it to a repair shop.

Well no, the WiFi and GPS antenna are different. YES the location tracking on an iPhone usually works using WiFi hotspots (accessing them to track your location). But no it's a different component, if the GPS isn't working it's most likely something wrong with the location services, or the IC of the logicboard (Murata 339S0228 Wi-Fi Module is on one side and Qualcomm QFE1100 Envelope Tracking IC, RF Micro Devices RF5159 Antenna Switch Module and Skyworks 77356-8 Mid Band PAD on other side of logicboard, see iPhone 6拆解 for more info, btw in case you need to replace, see iPhone 6)

According to one of our teardowns at iFixIt, the LCD is connected using ZIF connectors, which stands for Zero Insertion Force, meaning you can insert the cable with very little force (Citation from wikipedia: "The two sliding parts of the connector are then pushed together, causing it to grip the wires"). So no need to worry about any locking mechanism for the cables. If you mean coming directly from the SiP, those I don't know of any replacing method or locking mechanism

After doing some research I can conclude the following, According to few forums and google support, the Home Mini does not have a integrated battery and only works using the 5V 1.8A adapter. None of the Google Home products feature this anyway (Which does make me wonder why you'd think it was rechargeable before) So basically, sorry but no it does not have a rechargeable battery. HOWEVER, the Google Home (standart, not mini) has an option to get a "portable battery base", which gives 8 hours of use (Info found here: https://www.cnet.com/news/add-a-portable-battery-base-to-your-google-home-for-38-95/ )

@jayeff I guess it was a driver failure after all, I don't know whether this will occur again but I uninstalled and then reinstalled the driver for the touchscreen, now it works properly (Though I can't confirm if it's permanent or temporary fix as it's only been 38 minutes since driver reinstall)

Actually, in this case, there's only 2 options here. 1. Check if there are no damage to the cables inside or if they are dislocated. (You might want to check if no other components are damaged aswell) 2. Buy a new screen if you've confirmed it's the screen, not the cables (In that case just buy new cables). (Note if you can't do this yourself, I'm sure there's a local repair shop that can do this, you just need to buy the components that need to be replaced (If they don't have them))

There's only few logical problems in here: (1) Your SSD is corrupted (2) Your SSD has been damaged Best solution here is to try with another drive to boot, or get a new one if you still have warranty on it. If the drive is still detected but won't read, write, boot, repair, etc, then your drive is corrupted and can't be used sadly as this is a problem that can't be fixed most of the time. If you can, try to at least get important files from that SSD using your other Mac if that's still possible.