Yes but they are not treated so make sure you prime and paint them
It would depend on the size of the playhouse. If it's a miniature playhouse, I would say it's just fine. However, it you're talking about a full size playhouse where kids can actually go inside, then I would use 2" x 4"s.
Yes 1 cut is no charge
Yes. Lumber associates can cut wood to length on the radial arm saw, at the back of the department.
HI, you need to contact your local home depot you would be getting the wood from, ask for the pros desk then they can give you all bulk purchase information.
Yes this works great for this
I would not, they are fairly weak under their own strength and will bow very easily.
yes I think its 25 per bundle
I think they would work very well for batting
Yes for one or two seasons