can i tile straight on plasterboard?
if you want to do a proper job and not cut corners like most jack-legs do.you must apply a product called hardy board over the plaster and be sure to screw into the wall studs.then apply your tile on top of that.it will last a very long time and you will feel proud of a job well done.
Not a good idea. Tile needs to be attached to a stiff rigid surface. While putting tile on plasterboard will work, it won't last a long time.
Yes - our bathroom has survived 40 years straight on to plasterboard. Provided you grout properly and seal along the edges of the fittings you'll be fine. Whatever you do, don't think it'll be a good idea to use PVA as a primer - it goes all gooey some time later and the tiles drop off. There's a website about that issue somewhere, but I forget where.
You can if it's not in a shower, or other location subject to high moisture and it would be best to roll on a primer/sealer first.