I got into an REU on the 2nd, I have a week (the 9th) to accept/reject. I applied to 14 other programs, and I'd like to hear back from as many as possible. I applied to most programs the mar 31st/april 1st, altho several of them i applied to a week or more prior. They're largely rolling admissions, so I'm not sure if this is a soft rejection. Several have deadlines OF the 5th, so i shouldnt have heard back regardless.

A) When should I hear back?
B) When should I email programs for a follow up (I was thinking tomorrow but this might be too soon)?
C) Should I let these programs know I've been accepted into one for the followup email, so I'm trying to choose?
D) Should I respond to my current offer before the deadline to let them know I'm honored/interested and am waiting to hear back from some others?