got simple literature ,but mostly u need to teach her urself,im sure it will took some time(as i did to my parent)

1. i dont think miui need anything beyond what already in the box,just tell her to buy a beginner guide/pdf for android user,so better,install simple launcher to her phone and let her play with it
2. just use it as it is,no tweaking for mi3,it already have great battery,if u curious ,there are performance,balanced,battery saving mode,just keep it default
3. yes
4. in my case,no actually,but alot of ppl having problem with that,mine works just fine
5. what issue? ur mom use it right?how secure u want?

2. battery saving mode,but that is laggy and defeat the purpose of own a snapdragon 800 device
5. errr,my whatapps work(display pic) from v14,v18 and dev roms, mi3 shipped with v14,so,as long as u dont update it to v22,23,should be allright,just wait they solve it

i asked before, RM10 -- 

There's a read me app ready in the Miui phone. It's the soft copy of manual. Check it out.

Compare to mine, I can tell the short one is the original since mikey button have a step down.