Astroturf garden decking

Hi yes you can as long as all decking is solid it will be fine

Yes you can, there is no problem in laying it on decking.

Yes, artificial grass can be laid on top of timber decking. The decking will however rot prematurely, especially if the more common latex backed grass is used, reason being the latex backing holds water like a sponge even although it will have drainage holds. PU backed grass on the other hand, the stuff that's normally used for dog toilet areas is a better solution as the backing doesn't absorb moisture.