JEE

Your 11th marks doesn't matter in JEE all that matters is how well you have performed in JEE and whether your 12th board marks are above 75% or not.

If you have scored 75% in 12 board and determined to get into IITs or NITs you should take drop and achieve what you want.

JoSSA is the counselling body of JEE Main and JEE Advanced so in same preference list you can apply for both NITs and IITs and depending on your preference and rank and seat availability best one will be allotted to you.

You can expect some lower NITs with lower branches also you have good chances of getting decent IITs with good branches so don't give up and participate actively in JoSAA.

With these marks it will be almost impossible to get admission in the college.

The percentile which you got is very less as compare the percentile required to get admission in IIT and NIT.

Yes you will be able to get admission in UPSEE college for most courses.

SRMJEEE Rank holders of 1 to 100 - 100% waiver of Tuition fee, Hostel Fee/Transport Fee
SRMJEEE Rank holders of 101 to 500 - 100% Tuition fee waiver
Children of Defence Personnel - 25% Tuition fee waiver.

No u may attend special round, once try your luck.

May be you have a chance to get in government college depending on cut off. But not in popular government college. It is quite difficult to tell you about the cut off as it depends on various factors like: Number of aspirants appearing for the exam, Number of aspirants applying for the exam, Number of aspirants qualifying the exam, Difficulty level of the paper, Previous year cut off trend
with a sc category rank of 20,190 you do have chances in government colleges but you won't get into top branches or top colleges. You would have lower and newer NITs, IIITs, and GFTIs.