Firstly, I'm sure many people have done exactly that. No one (to my knowledge) has ever reported here that they have been marked void with one very low mark. I don't know how they judge it but if you have a go you should be alright. Indeed I bet if you have a go you will score a lot more than you think you will. F3 always feels worse than the marks you get.
Secondly, F3 has next to nothing to do with F1 and F2 (in terms of assumed knowledge) and has more in common with the 1st 2 levels of the performance pillar. It is a difficult one to understand but don't feel it's because you missed out on studying F1 and F2... they really don't help.
Good luck.
