Post [Q] Help me with MIUIv5 3.12.21 for a110

i did everything, flashed 4.2 kernel, installed MIUIv5 3.12.13 then patched update for 3.12.21 and i have the following problems.
1. camera only works for front.
2. i cannot install any app from play store. i can't even install from a backup i had. it says error while installing "-110" or something like that.

i really like MIUI rom but i can't use it since i faced many problems.

Help me

Thanks in advance