My wife just got a targeted 100k/10k biz plat offer in the mail and does not seem inclined to use it

Question1: Can someone else (me) use the RSVP code for a differently named business?
Question2: Anyone have experience holding BOTH biz gold and plat at the same time for the same business--what does Amex policy seem to be on this?
Question3 (sorry sort of new to MR): Do biz cards count against Amex card limits?