We have a finished attic that will be used for a bedroom, bathroom and closets. It has 6 to 7 foot knee walls on the two longest sides of the space. Behind these knee walls we have put plywood on the floor to give us attic storage space.

I was wondering if I can use wire staples to tack the wires along the back side of the knee wall studs (inside the floored attic space) when running wires to outlets that feed the rooms or do I have to drill through the studs?

Is there a specific spacing for staples when used like this. I am planning to staple to every third or fourth stud?

And can I mount junction boxes between the ceiling joists in the attic space?

Sure what you propose is fine, Romex cable needs to be supported every 4.5 feet.

Any junction box opening must be accessible and not covered by floor or wall finishes.

Thanks again tkrussell.