Can it a CPU damage the mb?
What do you mean by overheating?
You can check the VRM MOS temps in HWInfo64 - even the most power-crazy boards pushing insane wattage into i9’s don’t get higher than like 60 or maybe 70, so I highly doubt your mobo will get damaged from whatever you’re doing (generally, the auto’s or even maxes in bios are not, generally, capable of damaging your mobo over a short term).
Modern motherboard above a certain quality can put up with a lot of abuse before things go wrong, ignore lemons and situations like that.
I received this i9 from online auction for the cheap price and now thinking about worth it or just sell back.
You could run it at 99ºc, 24/7 for 5+ years no issues they don’t care. Like them or not, Intel makes solid products.
No it’s just going to throttle
I will take a picture bottom surface of i9 12900k soon and upload to it.