Yes. The plaster has to be damp to wet and in a place where air does not circulate. Mold will grow even faster if the damp plaster is in a semi-lit area. There is no real way to kill the mold once the plaster is completely saturated with water. It must be replaced. Otherwise, a strong solution of bleach will kill the mold and mildew spores.
Yes if you buy a house that has been neglected for years then it can,any wall can if not cleaned right