screen flickering/flashing after cold temperature

Hello, few months ago i changed the motherboard of my mac, old one was damaged and graphics card wasn't working, so i was happy until one day, now before it i should mention that:

screen flickering was common on this machine before changing motherboard, screen flickering was appearing as soon as machine was using burned out gpu, and flickering was simply fixing, after you turn off automatic graphics switching

But now, flickering appeared quite unexpectedly, one day i just brought my mac to school, it was freezing cold out there, and cold somehow did something to my mac, is started to flickering again! Also warming up isn't helping much, sometimes i run windows w spintires on it and it still doesn’t heps much

also the next detail that's confuses me so much, after i tried to downgrade my mac to older version of macOS, i found out that there wasn't any stability or anything that was holding me from upgrading back to catalina, so i got back to catalina and the flickering was go e, i thought by deleting all the system files and installing new fresh os might have done something, cuz it was looking so.

But suddenly! Few days ago i bring this machine to school, it was also cold outside and mac started flickering again! The flickering in question looking strange to me, im guessing that this is because machine tryis to change graphics between integrated and discrete graphics but im not sure, but the thing is that i believe is that, this problem comes back after cold weather/temperature Stuff to mention: this mac has bad battery, something like 68% of health, screen has several missing pixels (i asked some ai and it said that it might be battery problem idk )

Im wondering now, should I continue to invest money in this? Like it still got kinda burned charging port that i wanted to replace, and also the battery cuz i like the idea of 5hours of work, if its really battery the issue ill be happy cuz i can just buy it and replace,

Also don't ask me to do apple diagnostics, its just dont work on this mac, also tried resetting vram and smc, its dont works

so like, this flickering appears from the botton of the screen and from the top corners, also may appear from bottom corners too, looks kinda like old video processor trying to process some heavy picture

forget to mention!!!! while watching youtube videos on safari, entire screen color shades is changing a bit! every 3-5 seconds, also!! color scheme..? is changing everytime i change screen brightness or keyboard light brightness, so as i guess its some video graphics problems

small detail, when time passes and flickering kinda fades away, its fading away from left to right side, left side of screen might not flicker but right is still flickering, all the time it happens the same way