I don't see why not, you will find it difficult to get moss in any large quantities unless it is the sphagnum stuff which is dry and in a bag

i dont see why not either. they dont have roots so you will need to keep it misted/damp but dont over water the tree.

Moss on bonsai is there primarily for aesthetic purposes (as a representation of grasses). Don't allow it to get too thick as this can suffocate the soil and it can keep the growing medium too wet in winter and too dry or too wet in the other seasons.

To grow moss on your bonsai find some emerald green moss (it looks the business) dry it totally then crumble it onto the surface of the growing medium. Keep the surface damp.
Growing moss on indoor bonsai is nearly impossible as moss needs cool damp conditions in which to grow. You may get some results if you keep the powdered moss covered with a sheet of plastic after watering.

Moss from the garden can be used, but use an attractive one and utilise it in the method described above.
I hope this helps. If it didn't, at least it gave you something to read. ;-)