about spaces

I read all forum posts about spaces what I understand is it is a container like groups, but it can include other spaces, groups and posts.
My question is all other modules like forums may be included in spaces?

Good examples are:

a space for a hospital and subspaces are clinics
a space for a university and subspaces for faculties and groups for graduates
etc.

1. May these sub spaces have their own instances of
discussions ?
groups?
posts?

2. can we as the administrator move a group  into a space after group was created? Like we have a hospitals space but someone created a clinics group out of this space?

3. Lets say we have a hospital space and a clinic subspace, can the clinics subspace create groups in it?
another example:
Photography space
                     Nature Photograps subspace
                                          Mountains group ? (is this level possible?)
                                          Canyons group ?
                    City Photograps subspace
                                         Istanbul group ?
                                         Moscow group ?
                                         St Petersburg group  ?
                    Photography technics subspace              
                                         
                                     

4. I didnt see spaces in the power app list is it included in the 50/month application list?