Hello Candidate,
For BTech, Candidates need to secure minimum 75% marks in class 12th or equivalent exam or be in the top 20 percentile in their class 12th exam conducted by the respective board and  SC/ ST candidates need to secure minimum 65% marks in their 12th or equivalent exam.
For BArch and Bplanning candidates need to secure minimum 50% marks in PCM subjects in aggregate and 50% individually too.
All the best :)

Hello,dear

Yeah ! It's necessary to score 75% if you are from cbse board and if you are from other board then your marks should be in top 20 Percentile .visit the below link to see full eligiblity criteria of jee in detail

https://www.google.com/amp/s/engineering.careers360.com/articles/jee-main-eligibility-criteria/amp

hope so it will help you!!all the best