CBSE 10th

As there is a huge gap now between your academic qualification, getting in a regular course will be a challenge. I would recommend you to join NIOS for your 11th and 12th.

Yes, you have a fair chance of getting a GD-PI call. There are a lot of students every year who perform well in GD-PI and convert despite their low score in entrance exams.
Good Luck

You are eligible to apply for MBA Anna course if you don't have any history of arrears. Your marks are fine. If you have any work experience, you can apply for PGDM, which is considered to be the flagship course of PSGIM.

Most probable yes, you have to produce all the relevant evidences during the counseling process and also write as well as contact to NCHMCT regarding the mistakes occurred immediately.

Yes, you are eligible. The minimum marks requires in class 10th for Diploma engineering programmes is 35% in aggregate. Further, the admission are done through the common admission process (CAP) conducted by DTE Maharashtra. Hence, participate in CAP round for admission.

In order to pursue any degree, you need to complete class 12th.

There are so many courses available in the study circle:
I would like to refer that you can join hotel management and aviation courses that builds up your future all so.

Actually, whatever course you try to enroll after completing class 12th, they ask for minimum 50% of marks. In this case, you don't have that both in class 10th and class 12th. So, chances are very slim. Still, it is okay to try your luck but trying after improving your marks would be a better choice from my side. All the best.

In case, you did not mention your roll number/name on supplementary sheet and enclosed the sheets well, you need not to worry. Otherwise, there is no solution to fix it now.