The ball head can be unscrewed. Underneath is the screw with the same thread as the tripod thread of the camera. I don't know what thread Manfrotto has.

Yes, that is possible without any problems. As far as I have seen, the Manfrotto head also has a standard thread at the bottom. There is even the option to buy just the stand without the head from Joby: Joby GorillaPod 3K Stand.