What happens if you miss a colleges regular decision?

You have to check if they have rolling admission. My school, for example (Penn State) has that kind of admissions process where priority deadline for freshmen is November 30th, but you can still apply year round. It's always best to make it before the priority deadline. It makes your chances of getting in a lot better too.

It depends on the college, there are many different policies regarding late applications. Some will not accept late applications, some will accept late apps only if there is space available, some will accept late apps but they will not look at them until after they look at all the apps that were on time, if there is space. Look on the website of the college you are interested in to see if their policy is stated. If not, email them or give them a call and ask.

Good luck!

Most likely, no. That college should have information about it on their page.