could they possibly let me on the course?

basically due to certain circumstances I couldn’t properly do my gcses because I have been out of mainstream education for the last 2 years which means I only have 3 gcses.

the course I want to do in college has has the entry requirement for 4 gcses

would it be possible if I could resit my others and do this course btec level 3?

Firstly, have you spoken to the admissions officers at the college to explain your situation? If you haven't, it's good to check before you do anything else.

Secondly, even if you don't have all the necessary GCSEs, the college can sometimes allow you to resit a few GCSEs (or at least the key ones) in order to make yourself eligible for the college. It's also worth asking this.
Do also note that if you're under 18, education through offline mainstream colleges is often free, so I would try to sit the GCSEs through a college or adult college for free where possible.

Thirdly, if you only have 3 GCSEs, do you want to do GCSEs in other subjects as opposed to just resitting the ones that you did? If so, you can often do GCSEs within the year to make up for the difference in marks.

yeah I am sitting a few other gcses next year as a private candidate and I am going to talk with the admission officer tomorrow, I am more so worried i will be rejected from the course because I am missing one grade