CBSE 10th

Try to score as high as possible in CAT if you really want to do an MBA. That should be the first step. It is not impossible but would be difficult considering 12th and graduation marks. But if an MBA is the way ahead, first focus on CAT and leave this aside.

Yes, you can get admission in Diploma courses on the basis of 10th from NIOS. Because NIOS courses are valid at par with education boards courses.

Yes you can do the PGDITM course of SCDL Pune. The eligibility criteria and other details are given below.
Eligibility criteria : Bachelor degree holder / Graduate in any discipline from a recognized University.
Course duration : Two years
Course fee : Rs 46000/+1000(Application fee)
Fore more details please visit http://www.scdl.net/

No this will not affect in MBA placement drives. The placement drives are conducted on the basis of CGPA/ Percentage obtained in whole MBA courses.

Yes, you can take. The eligibility criteria of B.Sc (Hons. ). Agriculture through ICAR AIEEA UG 2020 is class 12th with a minimum 50% of marks in PCB/PCMB/ PCM/Inter-Agriculture.

The eligibility criteria of DMS IIT Madras for MBA course is Graduates (or professional qualification equivalent to that of a University degree recognised by the UGC) in any discipline with first class or 60% marks (55% for SC/ST/PD) earned in their degree from a recognised/reputed University. IIT Graduates who have obtained a CGPA of 8 and above on 10 are exempted from the CAT score. So your academic profile is good enough for DMS IIT Madras for MBA course. The expected CAT cutoff for DMS IIT Madras for MBA is above 98. Hence, you have to score above this.