The hybridation is possible from all the orchids of the same specie?
 

Or only between some variety of the same species?

Orchids are special for that they have very weak crossing barriers between species (probalby one of the reasons for the huge diversity). I don't know of any family / genus of orchids where hybrids are not possible within the family / genus. But I can imagine there are some. An extreme example is the cattleya alliance where very complex hybrids between different genera are possible and fertile.

Interesting.
Cattleya Alliance Species and Hybrids
From now on i would like put more attention at the note about the parents of Hybrids.

Where i can find information about hybridation?
For example here said that the Brassavola nodosa transmits it to his descendants: