help and advice please

[connors12345]

tiling an old dears bathroom next week and am putting ply down first with a flexi rapid set adh and flexi grout. do i apd prime first? the floor is 3.5 m2 do i put the ply down in one piece? how do you go about cutting around pipes etc waste pipe?do you just cut a square out and put pieces around the fiddly bits? also i know you are supposed to use 18mm ply but what do you all use? the floor at the moment is t and g warped which is slightly warped. could you use hardie backer board 12ml or is this unsuitable
thanks your help appreciated:mad2: is a 1 part flexi ok or 2 part