Return it? If that is school property, then that belongs to the school.

remove hard drive and put a new one in.

Did you get a refund for it? If you did, apple can lock the device remotely. If you did get a refund, then you did not lose out on anything unless you want a free item because of what happened. Once it is locked, there is no way it can be fixed for cheap.

get a carbon monoxide detector and check for levels.

put the tv on a smart plug. You can then tell it to turn off remotely or set a routine for when it turns off and on

That is normal for an i9 and a laptop. If you hit 100c all the time, then get worried. Even so, the computer will be smart enough to roll back vcore to cool the machine. If for some reason this still does not cool the machine, your laptop will just freeze or turn off to prevent serious damage.

if it is a gmail account. You can reset it by the google account. You can sell it after doing a factory reset but disclose that it is a locked phone.

When you say public wifi, do you mean like the library or from restaurants? If so, they can control what traffic they allow on their network and can blacklist traffic from VPNs.