hi,

see from 2021 gate , which conducted by iit bombay, it is stated that students who are in third year of their studies or have passed 3 years bachelors are also eligible to apply. A candidate who is currently studying in the 3rd or higher years of any undergraduate degree program OR has already completed any government approved degree program in Engineering or technology or  Architecture or  Science or Commerce or  Arts are eligible to apply for gate.

so your eligibility condition would not differ than other stream candidates.

the syllabus for XH - humanities and social sciences is as mentioned in below link:

https://cache.careers360.mobi/media/uploads/froala_editor/files/GATE_2021_XH.pdf