need advice if job has been done properly

What do you mean by drywall if you mean direct to plaster board then thats ok its better than tiling to plaster skim,but as for dot and dab well thats a no no as you will have to many voids under the tiles cant see why hes done this its just as easy to trowel the wall and gives you a better fix do not pay him until hes done it right then again get a pro tiler to do it right.

Personally if it was me i would be getting a different tiler in and charging the first one for the cost to put right !

Tiling to drywall is a no no. Dot and dab is a no no. Tile adhesive to fix wooden skirtings is a no no. Your should have employed a tiler to tile and a carpenter to fix skirtings. I really hope you haven't paid the person.

Absolutely no problem with fixing tile to drywall, as long as its firmly fixed to the substrate. Also providing the finished weight of the product. If its ceramics or porcelain then you should be fine. Spot fixing on the other hand is not an acceptable procedure! Yeeha springs to mind! Skirtings should have been fixed with an appropriate grab adhesive although I doubt you'll have them falling off the wall with tile adhesive. Not often you'll see tiles randomly dropping off walls, unless of course they have been spot fixed :) Pay peanuts get monkeys :)

Tiling to drywall not a problem, you can prime the bare plasterboard first if you want, Tiling with little adhesive means tiles could full off after jobs complete, it sounds as though his not a tiler but a cowboy, he has obviously not bought enough adhesive . Regarding skirting you can fix it with a good grab adhesive like gripfill but not tile adhesive, DO NOT PAY!!!!!!!!!