hello ,
let me inform you both papers of tier 1 and tier 2 are conducted online on the same day but the may conduct on different dates. the is no offline paper so you had to prepare well for online paper. but tier 3 is decriptive so itis conducted offline pen paper based.
Each paper contains 100 questions of 2 marks each and for 1 wrong answer you will be awarded -0.5 marks.