I had concern about Paradise and Hell.
1) On what basis paradise and hell will be given?
2) Our Scholars say that if someone doesn't believe in wilayat of Imam Ali ibn Abi Talib (a.s), they're not going to enter jannah. Is it true?
Other sects in muslims they obey Allah (swt) and his Messenger (pbuh). Just because we have different jurisprudence and not believing in Imamath they are not entering jannah?
3) In the grave will there be a question like who is your Imam?

1. The basis as per the teachings of the Quran and prophet is Obedience to Allah
2. This is true so long as it’s intentional. Meaning the person knows the truth and intentionally rejects it. Others will enter jannah so long as they are sincere in what they are doing.
3. Yes there will be questions about Imams in the grave