(Solution for models with removable RAM sticks) The issue you're experiencing is due to the CPU overheating, which causes the solder connections on the "SLOT A" memory RAM to become soft and detach from the motherboard. When you disassemble your laptop, you may notice melted rosin or flux residue. Unfortunately, there isn't a permanent fix for this. One temporary solution is to apply pressure to the top of the RAM holders to try and secure a good connection, which might prevent the laptop from displaying the "2 amber + 4 white" error code. However, the best option is to use "SLOT B" and upgrade the memory stick in that slot. I hope this helps! Gosh

All you had to do is press and hold the power button for 2 minutes and it would've reset the battery state and come back to life. It's a typical behaviour of any iPhone once the battery has been replaced... I know it's too late for you now but let's leave this info here for others to benefit.