Hey Anubhi,

IIT Kharagpur, IIT Bombay, IIT Delhi, IIT Madras, and IIT Kanpur have dual degree courses. But, you will have to apply on the basis of 12th and give JEE mains. Only than you can get Admissions in IIT dual degree. But this will waste your B.Sc years. If you have just started your B.Sc than you can quit and apply for JEE mains April session 2020.

You can do M.Tech after B.Sc but only if your BSC is of 4 years duration. After BSC, you will have to give GATE examination and than get admission in Mtech in IITs. The duration for B.Sc has to be 4 years because the minimum eligibility criteria for GATE states that. Otherwise, you can complete your M.Sc and than you can apply for GATE.
Master's degree in science, mathematics, statistics, computer applications, etc is accepted.
Moreover, you have many more options after B.Sc as well, but still if you want to enter into Engineering field, than you will have to look forward to above mentioned criterias.

Hope this helps!