Tablet won't let me open anything. Bought from a garage sale and she reset it and now it won't work. I tried opening google play and it still wouldn't connect

Because you keep getting "an internet connection error" it sounds like it is not connected to the internet. I would try to address that problem first. I would go in and delete the wifi connection and re-add it using the correct network name and passphrase for your wireless access point. I think that once you get the internet connection error to go away, you will have better results with internet-dependent functions like the app store. Also make sure you don't have airplane mode or other feature activated that would turn off the wifi.