JEE

No, JEE Mains scores are not compulsory for admission to BTech courses at SRMCEM Lucknow. Because the college also accepts CUET UG scores for admission to BTech courses. However, 85% of the seats for the BTech course at SRMCEM Lucknow are reserved for the candidates who secured valid scores in JEE Mains, followed by UPTAC counselling.
Hence, one can say JEE Mains is not the only entrance exam that is compulsory for admission to the BTech course at SRMCEM Lucknow. However, it is one of the considered entrance exams. 

Yes, candidates can get admission to Padmashri Dr. Vithalrao Vikhe Patil College of Engineering (PDVVCOE)'s BTech programme with a valid JEE Main score, given that they have cleared the cutoff set by the college. 
Candidates wishing to get admission to the BTech programme can use their JEE Main score or their MHTCET score for admissions. 

If 48870 is your OBC NCL ranks then it is hard to get any sourse in NIT Trichy or calicut. If 48870 is your AIR rank, still you will not get any branch in above college. You should try somewhere else.

Yes, an EWS certificate can potentially help you get admission to B.Tech ECE at IIEST. With an EWS rank of 6918 and 96.7 percentile in JEE Mains, you have a good chance of getting into IIEST Shibpur, especially for ECE, though it may depend on the specific cutoffs for that year. Your 96.7 percentile and EWS rank of 6918 indicate a good performance in JEE Mains, placing you within a range where you may be eligible for admission to IIEST Shibpur, especially for ECE. 

For integrated M.Sc. programs at both CET Bhubaneswar (now OUTR) and VSSUT, admission is primarily based on OJEE counseling, with JEE Main scores also considered for some seats. Candidates need to appear for both OJEE and JEE Main and then participate in the respective counseling processes. The final seat allocation is based on the merit list prepared by OJEE, considering both OJEE and JEE Main scores. 

With a CRL rank of 358800 in JEE Mains and being in the SC category, it's unlikely to get into NIT Durgapur for most popular branches like Computer Science or Electronics. However, you might have a chance at other NITs or branches with lower demand. It's recommended to check the previous year's cutoffs for NIT Durgapur, specifically for the SC category, and also explore other NITs and government colleges that might be a better fit. NIT Durgapur's admission is based on JEE Main scores and the JoSAA/CSAB counseling process. The cutoffs for popular branches like CSE and ECE are typically very high, even for SC candidates. 

Assuming 50 marks in the JEE Mains, your percentile would come to be around 70-75 percentile. One should keep in mind that the specific percentile may vary annually due to such factors as the level of the difficulty of the exam, the number of those who took it, and the overall results.