Hi, why can't I install apps on my Samsung Galaxy S2 I9100 ?

[AC Question]

I hard reset my phone and erased all USB data because some apps were installing without me knowing it. When I reset it I just couldn't install apps,my playstore is now some old version because of reset.When I try to install facebook it stops and says 406 ERROR,but when I try to update youtube because youtube and google come whit device it does update,and I can install some apps like FIFA 15,FTS 15 but I don't need them also sometimes it says 927 ERROR.I tried everything whiping cache and data on playstore,reseting phone again downloading from google but it says that there is no app on phone.Please help I don't know what to do anymore.