Help with primers

hi guys i am re tiling my bathroom, tanking it and putting up a new shower. I was going to replace the existing shower with a bar mixer. I have primed the shower wall and back wall with tanking primer and the far wall with mapei plaster primer as i wasnt going to tank this wall.

However now i have found out that i can buy thermo mixer shower/bath unit that can go onto the bath taps , this will make life much easier as my tails are to short.

Now i am confused with primers, can anyone experienced person answer these questions?

- Can i apply aquaseal tanking membrane onto mapei plaster primer??
- Can i tile directly onto aquaseal tanking primer using keraflex mapei powder cement addy?

- If i cant on, can i apply primer onto primer to resolve it?

Much appreciated