Restoring a Broken $2 Tetris Handheld. 9999999 Games in 1

I bought this old broken Tetris style brick game hand held console for restoration for $2. You can also buy similar devices new for the same price, but sometimes it’s about the journey, not the destination. I don’t know what math they used to calculate the promised 9999999 games, but I think the real number is a bit under 3000, mostly different variation of Tetris. The console is badly yellowed and dirty, the audio doesn’t work, some screws are missing, and there is a lot of rust on the contacts. I started by disassembling the console. Somehow I was surprised how cheap it was on the inside. Not sure what I expected... I found the audio was missing because one of the wire was loose. I suspect some parent may have done that to make the device silent because the sounds were really loud and irritating. The wire was easy to solder back on. Second issue with the device was the corroded terminal for battery. This happens when a battery is left on the device and it leaks. This can sometimes ruin the motherboard but