You are supposed to fur it out first. - That means a thin wood frame, usually 1x4 on the concrete FIRST. - It is not customary to apply drywall directly to a concrete basement wall.
He plastered the drywall.
You use standard 1/2 inch drywall .
yes
Drywall
That's definitely a good idea. If there is a sink and tub in there,I would even use a concrete or fibre board to back them also.
They had no sheet panelling . Walls were plastered.
NO. -Concrete may be a 'dry' wall, however it is NOT Drywall.
cement board
If it is mould all the bad has to go
If the drywall is directly onto the concrete, drill into the concrete and use a shield and screw or there is a concrete screw called Tapcon that screws directly into the concrete without a shield and holds much better. If the drywall is on furring strips, either mount the banister on the strips or go through the strips into the concrete.
Basement Waterproofing averts water from entering into the basement. It is imperative that you waterproof your basement or else it could end in a failing drywall or other structural damage.
You either have to have it plastered or you can go a less expensive route and use drywall mud to give it some texture.