Wetroom leak remedial work - tiling help - Tile Advice

[Kinso89]

Wetroom leaked.

Former and first course of wall tiles removed. WBP ply on joists (shower tray yet to be fit).

Grateful for tiling expertise on upcoming predicament.

Photos explain the following better:

Corner shower - one wall masonry (stepped-render?) and other brick inside studs.

Plan is to replace salvaged tiles once shower tray in.

My questions are regarding prepping the walls for tiling:

1. 12mm backer board on "brick stud" wall, (No more ply? Mapei addy (which one, Keraflex?) and tile. Will the "brick stud" need priming before the No more ply is attached?

2. Masonry wall looks like it was previously tanked as was a wetroom. Looks like stepped-render in photo? Also short of space for backer board here (see photo). How would you tackle this hurdle?

3. Does WBP ply edges still need sealing if only supporting a shower base and not a wetroom?

Thanks for any help/input.

 

[Slippery]

the brick stud wall has no timber stud atthe end so you will need to screw/stick the wedi board on, so use some primer for belt and braces.
The stepped render is possibly from an old shower tray or something? this needs to be perfectly flat to the substrate, maybe stick a wedi board in there?
I wouldn't worry about the wpb as long as you know it's not going to get wet.
Tank all areas with some tanking fluid (mapei is available at screwfix for a decent price.)