Two questions about RSVP for the Finalist Summit

I have two questions about RSVP for the Finalist Summit.

(1)If We pay own expenses for air travel and hotel, Can we that are 4 members participate in the summit?
I understand that we receive the expenses of two members, and can't understand if we could add two members with own expenses.

(2)When should I reply to RSVP by?

Regards,
masashi