***** NOT A TEACHER *****
(1) I cannot give you a clear answer, but I can you an answer.
(2) I believe that you are 100% correct (at least in terms of American English).
(3) The team has submitted plans. I assume that the team submitted the plans
as a group. That is, the 10 architects did not individually submit 10 plans. The
team submitted plans that represented the group's consensus.
(4) Here is an example that many American teachers give:
The jury has announced its decision. The jury have now returned to their