Default [Q] L7 II P710 Tether and Upgrade problem

Hi everyone!
1. Wifi mobile data tethering is not working well. On the phone says active, but i dont manage to connect simetimes/mostly with my tablet (acer iconia) until i rename the wifi hotspot. Than it connects and goes for some times (like 15 mins), than it disconects again and keeps connecting/disconecting until i reename it again. I tried everything but didint manage to understand the issue. I had the same problem with lg l3, that is why i changed the phone. If anyone else has some ideas i would be gratefull.

2. Second problem is that i am unable to do software upgrade. Says the device is suspected of rooting, or smoethin like that. I have rooted the device ( framaroot ) for some reason, and used titanium backup to freeze some applications, beacause thec phone was loosing performace, than i realised it didnt help so i restored everything and unrooted and i did factory reset. Didnt have FCs afterwards but now i cannot update. Somehow they know i have had rooted the device. I heard for the option restore build.prop but dontknow how to do that.

If anyone has any ideas i would be gratefull! thanks in advance