Route towards criminal/forensic psychology

I would recommend having a look at some university courses you might be interested in and their entry requirements to get a better idea of the specifics. I'll answer this based on general Psychology degrees, specific courses in forensic/criminal Psychology will be similar as if you want a career in this field you'll need to do a BPS accredited degree and the accredited content makes most Psychology degrees pretty similar. Not all unis will offer a specific forensic/criminal Psychology degree, but there might be modules you're interested in on general Psychology degrees too so keep an open mind when looking at courses.
Broadly speaking GCSEs do matter for university, for example there might be requirements to have passed English and Maths, and I know that some more competitive universities might ask for higher grades in these subjects (e.g. for Psychology at Oxford they recommend you have 7 in GCSE Maths). The importance of GCSEs also probably depends on where you apply, for more competitive universities having a strong set of GCSEs across the board will be more important. They will also matter for sixth form or college, which again may have minimum grade requirements to study certain A-levels, this will probably vary from place to place so websites and prospectuses for sixth forms/colleges you are interested in should have this information.
In terms of sixth form vs college - I can't really help here specifically since my sixth form days were a while ago. However some general pointers would be to look into the options for post-16 education in your area, check which places offer subjects you want to do, go to open days to figure out if it is the right place for you. I would say having gone to a sixth form that was part of a wider secondary school the stricter rules and more structured study time than my friends had at the nearby college annoyed me at the time, but looking back I think being more accountable for my studies in that way was definitely useful for staying focused on A-levels.
To study Psychology at university, you probably want to do at least one science A-level subject - Psychology counts. I found Maths and Biology to also be very helpful for a Psychology degree. But you don't have to take all sciences, I knew quite a few people on my Psychology course who did History A-level for example! If you're more looking at alternative routes to A-levels I'm afraid I can't help much, have a look at the entry requirements of any courses at unis you might be interested in and see what qualifications they accept.

I am interested in studying criminal psychology/forensic psychology in the future. If you know the route i should take or are taking this yourself it would be helpful if you could answer my questions.

1. I am a year 10 and doing gcse exams next year. If i want to go down this route do i need to get specific grades for this? Will a sixth form or college accept me for psychology if i don’t meet standards?

2. Is it better to pick sixth form or college and what do you think is better, i know roughly some of the differences but not enough to decide what i think would be best for me. What is better such as freedom, structure, courses etc?

3. What do i have to get qualifications in if i want to go to university? I am interested in other subjects such as history so would i be able to choose that as an extra option?

I have a lot more questions but these are the most basic as i have no idea what i need to do or what i need to take. I understand that i have quite a long time before thinking about any of this but i don’t know if things such as gcse grades matter? Please could you answer thank you