GATE

The Graduate Aptitude Test in Engineering (GATE) is an examination that primarily tests the comprehensive understanding of various undergraduate subjects in engineering and science. The score is used for admissions to various post-graduate education programs (e.g. Master of Engineering, Master of Technology and Doctor of Philosophy) in Indian higher education institutes, with financial assistance provided by MHRD and other government agencies.

Hello Vaibhav,
Nowadays many people take a break and prepare for IIT's so there is no drawback in dropping, so it is recommended first you go for B.Tech from good colleges rather than thinking of GATE.

No, you will have to be a graduate first. Means you can appear in GATE after B.Tech and you can do B.Tech after 12th. GATE is Graduate Aptitude Test in Engineering. It is used to get admission in M.Tech, MS and PSU jobs. It is conducted by IIT and IISc every year. The exam is held in February every year and notifications comes in July.