8-Bit Ninja

You have a single wire from the fan plugged in? Any actual RGB Fan will have two leads coming off it

Yes you will

its not a mod, its just a chip that you pull out with your fingers and plug the new one in

If you email MSI direct, they may send you out a new BIOS chip instead of you having to RMA the board

What's the CPU usage like with you trying to watch movies on your phone and someone's using the PC?

You shouldn't need it installed, but have you tried installing a CPU and then updating the BIOS using the flashback button. You shouldn't need a CPU installed but no harm in trying

Regardless of if the BIOS is up to date or not, it has a BIOS flash button on the IO. So you could update the bios without a CPU installed at all

Take the card apart and look for anything with a burn mark around it

No hate, but why did you buy an i3 instead of ryzen? Also 16gb of ram and an aftermarket cooler on a small budget?

A good IPA bath would be my first priority after you do what @A1200 and throw that battery away. Its hard to tell from the photo but it basically comes down to whats rust from the board, and what's mineral build-up from the leak. Good luck man

I pretty much never recommend people actually do this as people panic from the results. But try running the pc speed test on User benchmark and see what the results are.

By the process of elimination it seems you have a faulty motherboard, if I were to guess I'd say something to do with RAM. Have you tried booting into windows on the x570 with your 5600x but only one stick of ram installed, and also moving the slot that said stick of ram is installed in?

No one can tell you the best OC for your CPU, You could take 20 of the same CPU's and they'll likely all overclock differently to each other. Just do as @Mixzzz said, keep the voltages stock and raise the core clock slowly, running a stress test after each increase, until it becomes unstable.

Have you updated the BIOS on your motherboard, some B550 motherboards (Mine included) wont post without a bios update to support zen 3.

Have you got another pc you could plug the graphics card into to see if it'll boot?