Can I start my graduation at IGNOU on my 2nd year if I completed my 1st year at another college? Can I do both BSc and another stream degree at IGNOU?

You certainly can. Credit transfer is available through IGNOU.

Credit transfer refers to allowing a student from another university to enroll in IGNOU to complete an equivalent degree based on credit transfer from that university. As a result, the student did not appear in the exam for that course, which was found to be equivalent to and for which appropriate credit was deemed to have been obtained for the purpose of fulfilling the IGNOU requirements for awarding a degree.

Of course, there are some ground rules. You can find it in the IGNOU prospectus or program guide. You can do both at the same time, one with a regular duration and the other with a certificate program. It would, however, be too difficult for you.