Trying to make an open-source project and need help figuring out how to flash firmware

I'm trying to make the following open-source board for a Panasonic 3DO RGB mod:

https://github.com/citrus3000psi/3DORGB

I have the soldering skills to put the whole thing together, but I actually don't know much about programming and was wondering if someone could help me understand how to go about doing so. My main questions are:

1. Which chips need to be flashed with the firmware?
2. Which firmware files go with which chips?
3. How to I go about flashing these chips and what equipment would I need?
4. I assume, I would flash the chips before soldering them to the board, correct?

I really appreciate any guidance. Also not entirely sure if this is the correct place to ask these, so my apologies if there is a better topic to place these questions in.