You are probably well familiar by now with how English forms 'tag questions' ( ... aren't you? ... ), but here is your chance to practise examples in other timescales and tenses.
Don't forget that ~ unusually ~ English makes rather more of a brief grammatical fuss than many other languages do over this everyday structure: we need to switch between an affirmative sentence and negative tag (or vice-versa), carry the subject agreement right through the sentence ('He has, hasn't he?'), and even put in a 'stopgap auxiliary', usually in the form of 'do' ('It arrives automatically, doesn't it?') if there happens not to be one already available.
With this in mind, let's hope your own Answers will indeed 'be OK'!
Answer 1 lacks the negative; Answer 4 has the sense of the past, but the wrong auxiliary and the wrong pronoun.
Answer 3 also probably reflects and reinforces the rather 'baggy' main verb 'do', rather than the original active auxiliary 'must'. English speakers may well refer to 'doing Pythagoras' or Shakespeare or whomever, rather than saying more specifically that they have studied geometry or read any particular plays.