When the SD Card shows that write protection is on in both ON and OFF position of the slider, it means that your SD Card reached it’s read/write resource, with other words - it died, and you have to get a replacement. Where did you buy the SD Card from?

Well, if the N64 isn’t displaying any image on the TV screen, you should try another TV cable, only if (I know that it’s a dumb assumption but, nvm) you’ve connected the RCA connectors wrongly, each RCA port from the TV has a color which has to be matched with the respective connector. If the AV cable replacement won’t help, you could try reseating the cartridge, or/and blow into it’s connector pins, maybe the problem is in cartridge’s old pins. If this won’t help too, then the problem can be in the console itself. P.S. Idk what HDMI adapters you’ve tried, but you'd better buy decent converters like same OSSC, because not every converter will output a decent quality on a modern TV.

If you want to clean the corroded spring, you could dip a cotton swab in isopropyl and rub it on the spring, it could help a bit. But I’d recommend buying new battery terminals, depending on which contact is corroded you’ll have to do a little bit of desoldering, as there are 2 contacts in the upper part of the battery case which are soldered to the gameboy’s circuit. The ones circled in the image below to be more precise. The squared ones are just terminals which can be easily popped out of the case and replaced, you can find them easily on the internet.

Well, the. Atom PD1 is a recommended charger for the Switch Lite, but I’d go with the original charger. On Amazon (as of February 24th 2021) there were a couple with the price up to 40$

Yes they are, the single con will be, that if you have other RAM sticks in that iMac, all the modules will work on the frequency of the oldest RAM stick, in your case - 1333MHz

Well, firstly, is the port working or not? You can try glueing that ring back in place, another option would be buying a USB card which could allow you to connect the mic through a USB port, or just use the ports placed on the motherboard, instead of those situated on the PC case

The problem can be solved by reinstalling the MacOS from Apple Recovery Menu. It looks like that SSD of yours has the settings of early 2013 model, which are conflicting with your late 2012 Mac. Yes, you’ll lose all your data (just do not forget to backup, or move to another drive, all important files, before reinstalling the OS), but you’ll have a normal working machine.

Problem resolved. The problem was in the console itself. The fuse which was responding for controllers’ work was blown, so I changed it, and now it is working smoothly

On the lower part, where’s placed the stylus, on the left side the should be 2 or 1 slots ( depending on the fact, if you bought the model with SIM card or not), lift the door of that slot, and insert the SD card as shown on the door’s pic

Maybe, try to change the flex cable, responding for R trigger, if it is not a physical problem?