can we submit building applications as a team, or do we have to work individually?
I think yes I may be wrong, wait for Sylvanor's opinion, even if you did the prize has to go to someone that will split it up, frankly we wouldn't know if anyone helped if you didin't tell us.
does that include vertical, horizontal, and diagonal?
Yes vertical, and horizontal, not sure about diagonal, ill let you know soon.
oh one final request for add-ons : -extra arches
-extra round bricks (Marconi pieces)
Im sure you can manage using other kinds of rounds instead of Macroni pieces, ill ask about extra arches, let you know soon.
EDIT: Follow up: Yes all poles allowed (vertical, horizontal, and diagonal), the rest no, use your creativity :D
Yes you can work in a team.