Hello Yashu!

ST(Scheduled Tribes) are considered as a whole different category.

The groups category 1, 2A, 2B, 3A and 3B etc. are sub categories under OBC(Other Backward Classes).

ST does not come under any of the sub categories of OBCs. But it is a separate category just like SC and OBC.

STs enjoy a reservation of 7.5% for higher education in Karnataka.

Hope you are clear!