NIT

Yeah you can get ECE in NIT Mizoram and EEE in NIT Nagaland, and CSE in IIIT Manipur. The best option I can recommend here is ECE from NIT Mizoram.

No, with an 83.5 percentile, getting Computer Science & Engineering (CSE) at any NIT is almost impossible.

CSE cutoffs at even lower-tier NITs typically require 97–99+ percentile, and top-tier ones demand 99.2–99.5 percentile

Yes it is possible infact there are very certain chances with a SC category rank of 9400 in JEE Mains, you have a very good chance of getting a seat in the Computer Science Engineering (CSE) branch in several NITs.

While securing a spot in a top-tier NIT like NIT Tiruchirappalli or NIT Surathkal for CSE might be very competitive, this rank is definitely within the admission range for many of the mid-tier or even some of the older NITs.

Your prospects are excellent and you can confidently participate in the JoSAA and CSAB counselling to secure a seat in a great NIT for CSE.

With a JEE Main percentile of 63.5, your Common Rank List (CRL) rank is likely around 3.2 to 3.4 lakh. At this rank,  getting admission into any NIT is highly unlikely, especially in the open (General) category.

There is not a fix number but several faculty members hold PhDs, including from IITs and NITs, especially in CSE and ECE.