Question

should i try the extra hard questions for maths exam

Answer 1

Hi,
"Practice make a man perfect"
Math is subject where the more you practice the better it is.So, practice more questions.
Extra questions are really important.
Your standard doesn't matter.Just practice more and more.

Answer 2

If you're worried about the cbse maths exam for class 10, I suggest try hard questions only and only if you've covered NCERT. 

NCERT is a must. And if you still haven't covered it yet then don't go for the hard questions right now. If you're done with NCERT and you've solved ample of question papers, going for some extra hard questions can be considered a good option. 

Don't worry much. All the best!