Delhi University (DU)

You can take admission in School Of Open Learning University of Delhi.

You can't change to B.Com now.

Yes. Delhi University started the 'special spot round' of undergraduate admissions for Candidates who wish to get admitted to the varsity This list will be for the candidates who applied for admission to the varsity through CSAS but have not been yet admitted to any college. To be considered in the

DU is much older and has much better ranking, accrediting and brand value. Ashoka University is emerging university offering courses in specific domain.
So these are two different sort of universities and DU is comparatively better.

Yes, definitely. There are various courses provided by University of Delhi that do not require Maths. You just need to pass the entrance exam or cut off for the course you need to take admission in. You can definitely take admission in BA Hons in Delhi University.

Yess the merit based admission are done for admission

There is a common entrance to get into Delhi University colleges i.e CUET.

No you cant take admission in two colleges at the same time. You can only take admission at a single college at a single time. If you want to take admission to another college you have to withdraw from the older and apply to the next one.

No, they simply allot you colleges list does not comes, but yes if you opt out from the 1st allocation next college is allocated to you.