You should not tile over wallpaper glossy surfaces lead paint or plywood.
Tile over plaster walls.
Also now it s been plastered you will be restricting yourself to a tile with a max weight of about 16 kg m2.
However tiling over tile can add quite a bit of thickness so make sure your wall can handle the weight.
Follow manufacturer instructions to a tee.
Add a diverter and shower line in the wall.
But with cement board.
Can you lay tile on plaster walls.
Adhesive grout and tile 20kg max weight onto plaster.
You would have to remove the plaster and replace it not with drywall run from a contractor who says that.
Testing the wall for durability.
Both painted and bare plaster allows for the installation of tile.
Mold does not grow on cement.
It used to be very common to put tile up on whatever the wall was and seal the the tile.
This was back in the 80 s.
Loose paint must be scraped.
Scrub the wall tiles with diluted degreasing cleaner and a nylon scrub brush.
If plaster is any way compromised you should tear out to studs and start over.
If you re not sure if you have lead paint test kits are available.
Or flatten walls with a latex modified skim coat product.
Cover with cement board tape off.
That is true you cannot tile over plaster if that s your plan.
The problem otherwise is that grout is porous and any slight crack will cause moisture and mold on any other surface.
Mix degreasing cleaner with water in a bucket using a dilution recommended by the cleaner manufacturer.
Not all plaster wall surfaces will support the tile properly.
I have repaired tile jobs that were over 20 years old that the tile was applied directly to regular sheetrock and plaster walls.
You may tile over existing tile painted or unpainted drywall plaster and textured walls.
Bring plumbing to code.