1.can we use calculator or extra page for basic arithmetic portion? Calculator not allowed and for rough work you can you last page of your question paper.
2.can we mark choices on question paper? NO
3.is there any negative marking? NO
4.what is best way to save time for confusing questions? it depends on you but i think 100 mins are enough for 100 questions. You may leave confusing questions and solve at the end.