Remove all tile adhesive, repair skim/finish to plaster wall, the wall need priming first. Leave to totally dry and then prime walls prior to tiling.
I would fix tile backer boards to the wall and tile onto that, here are some instructions for fixing to a brick wall ;
8. 1. Installation on brick walls
8.1.1 Preparing the substrate
Ensure wall is sound, clean and ready to receive HardieBacker®
250 cement board. At minimum, the rear of HardieBacker® 250
cement board and the masonry wall must be wiped down to
remove all dust.
8.1.2. Fixing sheets with tile adhesive, step 1
Bond HardieBacker® 250 cement board to the masonry walling
using tile adhesive. Apply tile adhesive to masonry walls using a
6mm notched trowel. The tile adhesive must fully support HardieBacker
® 250 cement board and the HardieBacker® 250 cement
board is firmly pressed into the tile adhesive.
8.1.3 Fixing sheets with masonry anchors, step 2
Use 9 pcs (3 rows of 3) ø 6mm x 50 mm masonry anchors with
self embedding head. The masonry anchors are immediately
fixed through the board into the masonry walls holding the
sheeting in place. Do not overdrive head of anchor, it must be
flush with face of HardieBacker® 250 cement board.
Note: Do not dot and dab tile adhesive.
8. 1. Installation on brick walls
8.1.1 Preparing the substrate
Ensure wall is sound, clean and ready to receive HardieBacker®
250 cement board. At minimum, the rear of HardieBacker® 250
cement board and the masonry wall must be wiped down to
remove all dust.
8.1.2. Fixing sheets with tile adhesive, step 1
Bond HardieBacker® 250 cement board to the masonry walling
using tile adhesive. Apply tile adhesive to masonry walls using a
6mm notched trowel. The tile adhesive must fully support HardieBacker
® 250 cement board and the HardieBacker® 250 cement
board is firmly pressed into the tile adhesive.
8.1.3 Fixing sheets with masonry anchors, step 2
Use 9 pcs (3 rows of 3) ø 6mm x 50 mm masonry anchors with
self embedding head. The masonry anchors are immediately
fixed through the board into the masonry walls holding the
sheeting in place. Do not overdrive head of anchor, it must be
flush with face of HardieBacker® 250 cement board.
Note: Do not dot and dab tile adhesive.
It would be easier just repairing the damage to the walls, rather than making a big job out of it. That is unless the basecoat plaster is also shot at?
