IPod 4th gen. troubleshooting

My IPod 4th generation won't let me use any internet anywhere I go, it crashes and shuts off. It overheats easily and I've been having trouble now for more then 6 months I've restored it 3 times and talked with and Apple rep. It won't update past a 6.1.6 therefore it won't let me download any apps that use the internet or any for contacting family and friends. I've had enough of it and now our school is opening up for more digital and it's driving me CRAZY!