One for all, and all for one!

to R55Max

I would like to clarify a few points:

1) Can I play against opponents from multiple teams simultaneously, naturally using my own pool of maps, or can I only play against players from another team after I have finished playing against the first team?
2) Regarding the selection of templates. What is the correct approach:
a) The opponent offers a choice:
8xm12 or 8xm12a
8xm8a
diamond
and I can choose any of the 4 templates (since in the first case, there are 2 templates in the group).
b) The opponent offers a choice:
8xm12
8xm8a
diamond
i.e., the opponent chooses the desired template from the group.