Ripping down plaster board to expose brick walls

[poomoo]

Hello,

I am currently in the process of ripping plasterboard from my internal walls to expose the blonde sandstone behind it.

3 questions:

Presumably the metal frame can be unscrewed at the bottom and top to completely remove it from the wall?

When it is all removed there will a 4-5 inch gab between the stone wall and the wooden floorboards. How should I fill this space and with what? Wood, plaster?

Finally, is it advisable to plaster the space around the windows?

Thanks in advance,

David