the phone was given to me with the expressed intention of me playing games on it because my boyfriend was tired of me always taking his phone. this phone has no Sim card so no calls can be made and it had no 3G.
i mainly play one logic game on here and have finished over 200 puzzles out of 800+ puzzles. again not a great reason to leave the phone broken but I'm not ready to delete all my progress yet.
as far as apps opening its usually things like Facebook or games that send notifications but i thought i had turned off the notifications. it kept opening apps that i never used before which lines up with what you said crews but it seems like i get a lot of game popups or games reopening themselves.
i just spoke to my parental units who have much newer Android phones (they just got phone updates) they both said that theirs get petty hot as well while they're using them. the house stays at a somewhat high temperature most of the day and despite having the ceiling fan on all day, my room trends to get the hottest. could that be what's causing it to overheat. (I'm not stupid. that just hadn't occurred to me until i found out that i wasn't the only one in the house with this problem)