For engineering, JEE Main is the national level engineering entrance test  for admission to IIITs, NITs & GFTIs and other private institutes.
As per the eligibility criteria of Jee Mains,
For admissions to NITs/IIITs/GFTIs, candidates should have secured at least 75% marks in class 12th exam or be in the top 20 percentile in the class 12th exam conducted by the respective boards. For SC/ST candidates, the eligibility criteria is 65% marks in class 12th.   

For B.Arch/B.Planning, mathematics subject along with 50% marks in total including five subjects.

Yes practical marks are being considered in the final result/total percentage calculation.

Hope this helps!

Yes, you have to consider you total marks including practical to calculate aggregrate marks.