I have two objects, and one is the parent of another. The reason of the parent relationship is that I want to apply different textures to each object. The two objects need to be bound, so I need to create faces between the two objects, but in edit mode I can only select the vertices of a single object. Can this be done? if not, what's the solution in my case? I need to separate the two objects somehow because I want to apply different textures to them.
Instead of parenting the object, you need to join them if you're going to connect them, select both and press Ctrl + J, doing so will make them two objects with separate meshes, you can now press Tab to go to Edit mode and work on vertices, edges and faces of both meshes.
You can still create separate textures, assign separate UVs to the same mesh.