Hi

Yes, you can do  graduation/ degree course on the basis of your 12th qualification along with your diploma , it doesn't matter even if you are in 2nd year of your Diploma right now.

This is because,

UGC has given its approval that one can go for pursuing two courses at the same time, the only condition is that one cannot pursue both these courses in regular mode i.e for both the courses to be legal, one  course can be in regular mode and other course in distance mode from Open University or online.

So, now that,

You are doing your diploma in regular mode, you can definitely do  graduation as a distance program , just make sure that you do it from recognised Open Universities like IGNOU , Dr. B.R. Ambedkar Open University , Vardhaman Mahaveer Open University etc

Thank you