Of the two recommendation letters, at least one of these should be from a faculty member familiar with your academic record at your UC institution. The other can be from another academic or someone familiar with your professional or volunteer work.
No. All materials—including recommendations—must be submitted by the deadline. Ask faculty for recommendation letters early, especially if they are on leave.
Yes. You must submit a letter of support from your proposed partner organization by the deadline. Ask the organization for this letter early, especially if their communications systems are not optimal.