Can I start a BA degree from 3rd year after graduating from another related BA degree

Not if you get awarded the first degree. You can’t use the same credits for two different degrees, (unless you have specifically been completing a dual award programme).

Alright so what would be my options on this? As I feel like I've wasted 2 and half years and what will be 3 years. Regardless if I get the degree or not. I went to uni thinking i wanted to do this as a career and to get a degree I'd use, however I don't feel I want to do interior design as a degree now and so will have a degree that I won't use.

Do you want to work in some field of graphic design?

Yes I rather work a job/career of graphic design than interior design. What re my options with my current situation?

See if you can find a masters degree in the latter area which will accept your first degree.

Or honestly just start developing a portfolio of independent self-driven projects in graphic design and build these up and put them on your own website, and use this as a basis to try and pursue roles in the field?

You don't actually need a degree in graphic design to work as a graphic designer in principle, it just gives you a structured environment to learn the "tools of the trade" and to start developing a network of contacts. If you can start networking now anyway through your uni, and otherwise learn key softwares and principles for the field and start building a body of work you can try and start leveraging that to get contracts.

Not the easiest or fastest route but cheaper than doing a second degree completely paid out of pocket (and likely cheaper than a masters).

I wouldn't be able to do a second BA degree. As no way I will be able to pay out of pocketed for 1 year of the degree, let alone all 3.

Masters I know is an option but I'm looking to see if there are other options too. I've done some research and master degrees don't teach you the fundamentals, BA degrees do. And because eive not done graohic design BA instead interior design BA which I've hated the whole time and not been taught any software, I don't have the skills for even the basics. I can't access Adobe software (that my uni graphic design BA and masters degrees uses and others) because they're so expensive for individuals to buy...£65 a month or near £800 a year and so my options to start creating a portfolio are very limited.

I feel very stuck and upset at myself because it will be 3 years (once graduated in summer...if I do..) wasted on a course I did not enjoy and won't directly use (as in go into interior design career) as well as near £60,000 in student loans (both tuition and maintenance loan for 3 years I've taken out)

Where are you studying at the moment that they don’t provide adobe access for interior design students?