list out comparisions between moodle 2.9.1 vs 3.0 or the earlies version and list out he points interms of improvements from the older one
Are you asking about https://docs.moodle.org/dev/Moodle_3.0_release_notes ?
Moodle 3.0 has the OU question types, so go with that.
Please have a look at https://docs.moodle.org/31/en/New_features.