From 5.1.1 Lmy47v & To ... ?

Sep 21, 2014
I got XIAOMI A1 with Google Android ROM but, after few months (last Google update inserted adv also on basic services like telephon call) I prefer to come back to my MI4S with XIAOMI ROM; my MI4s still has android 5.1.1 LMY47V and stable (LAJCNDI). What I have to do to rise ROM version to last stable one? Thank you.