firm is your first choice.
if you put a university down as your firm, then you meet the requirements of their offer when you get your grades, you have to go there (or nowhere)
insurance is your backup.
if you put a university down as your insurance, fi you miss the grades for your firm, but meet the requirements for your insurance, you can go there (or nowhere)
I'm pretty sure that the deadline for replying is long past though, unless you applied for medicine.
No I would not cancel the application, just it is so close I dont know what I want to do, I get the impression if I dont go to Uni I am going to be poor and living crap all my life.