Diploma

Yes who have passed 12th standard (any stream) from a recognised board are eligible to pursue this course.

Yes you are eligible. Please proceed further but follow the guidelines stated by NMC/MCI.

No, as you can't take two regular courses as per the UGC
You can take one regular and one distant course.

It depends on which stream you want to take admission. One of my friends got 9300 rank and he got offered in Jalpaiguri polytechnic college in ECE branch and if you are looking for the best university then it is a good university.

Cut off marks for admission to a diploma varies from one state to another state and also for different category of persons based on caste. In general, with special reference to Tamil N?du State, I can give the MAX to MIN% cut off for different category. However, this may vary slightly upwards or downwards.
OC and forward caste persons are varying from 100 to 80% of total marks in SSLC or SSC (10th class)
BC is varying from 79 to 60% of total marks.in SSLC or SSC (10th class)
MBC is varying from 59 to 40% of total marks.in SSLC/SSC(10th class)
SC or ST is varying form 100 PASS % of total marks in SSLC or SSC (10th class)

I can only answer for Faculty and the procedure of Technology and Engineering. Yes the branch for engineering can be changed under 2 conditions:
Reshuffling happens and you get promoted to a higher branch
You top the entire college ( including all branches) and rank in the top 5.

Well your work is commendable bu can you please be more specific onto what exactly your question is.

In Diploma here, the fees structure is very less in comparison to B.Tech. But Diploma is also less than B.Tech. So here you can easily get government Polytechnic colleges in every district one government college is available. So, focus on government college and the fees is 20k for the government college. And if you can go with the private college then your fees is something 1 lakh in RGPV university and this structure is only for OBC category and if you are a general category then your fees is 2-4 Lacs for Diploma.

Yes, you will get job.

Cut off marks for admission to a Diploma varies from one state to another state and also for different category of persons based on caste. In general, with special reference to Tamil Nadu State,I can give the MAX-MIN% cut-off for different categories. However, this may vary slightly upwards/downwards.
OC and forward caste persons is 100 to 80% of total marks in SSLC or SSC(10th class)
BC is 79 to 60% of total marks.in SSLC or SSC(10th class)
MBC is 59 to 40% of the total marks.in SSLC or SSC(10th class)
SC or ST is PASS % of total marks.in SSLC or SSC(10th class).