Someone please explain

I understand qualifying for Kona, but what about qualifying for the other IM races? How does this work? The way I understand it, if I want to sign up for IMLP, I could 1) sign up the following day at the race, 2) sign up online the following day 3) Get a qualifying spot from another race(Florida 70.3). Is this correct? Do they still give qualifying spots if IMLP is sold out? Would I have to race Florida 70.3 to get the spot or just be at the awards?
Thanks, KC

Yes
Yes
Yes, you need to race. Spots roll down the next place. If there aren’t a lot of people around, let might just ask who wants a spot (who raced).