Computer Science

Yes, you can get admission in B.Tech college without JEE score, but not in every college. Like every government college now has start considering JEE score. Some demmed University and central university conducts their own exams for students to get admission in different branches of B.Tech. Also almost every private colleges and private universities give direct admission and some conduct their own exams to get admission, but some reputed college conduct their own exam and also consider JEE score. Now there is common exam to get admission in government or central university which is CUET through which you can get admission in best universities which has very low B.Tech fees.

Yes, you can do M.Tech in specialisation of computer Science if you are from non CS branch. For this, first of all you would have to SEE particular college computer Science department M.Tech condition, most of college's CS department allowed some non CS branch students to pursue M.Tech from some of their specialisation, but not for every M.Tech specialisation. Example if you got good rank in GATE then IIT Delhi allow non CS branch GATE score to pursue M.Tech in some CS specialisation but not in everyone, also most of college's non CS department has their own some M.Tech CS specialisation like IIT Delhi electrical engineering department has M.Tech specialization in Computer Technology with EE, EC, IN GATE score
So first just check the particular college M.Tech brochure, in which they clearly mentioned that which branch of students can pursue M.Tech in any particular specialization.