What would make it not blow hot air & y temp gauge passes hot and flikkers

What is your question?

Three days ago went online found out may be pluged or air poket in lines blow into ? Wasnt sure but blew through one and fluid flowed back through port that i had hose from didnt know if it woul help but put it all back together still didnt work said ill check it out later so second day normal everything in n on the car changed oil and it went ok butt drove afte oil change noticed temp gauge was lil hotter than normal but went back to nomal park it today drove fine couple miles park it for few hours got in it was in a drive through n i looked down at gauges and neddle on gauge was past top line above hot and needle was flikkerring scaring me now please help one car family with three year old daughter thank you for putting up with my gibberish but thats wat happen