Hello Aspirant

Yes any student from any BTECH branch can write any gate exam for different branch.

Talking of difficulties as we already know that gate is anyways tough.The gate syllabus mostly have questions that are related to that particular branch.Because it is said that if you want to give gate you should be clear with all of the basics right from the beginning of your Engineering.

Therefore there might be a chance that civil students will find that exam more easy that other branch student.

But don't lose hopes there have been cases where Mechanical student have appeared for CS gate and secured an absolute great rank.

All you will need to do is a little bit of extra studies and you will be good to go.

Regards!