It's up to you

Yes you can, however, saying "I have to..." is a little stronger way of saying it than "I'm supposed to...". I hope it helps, :)

You can, but it changes the meaning. 'Have to' is not the same as 'supposed to'. If you say 'I have to', it would make this a much firmer obligation. 'I have to..' implies that there is no way that you can avoid doing the literature review. The meaning of 'I'm supposed to' is 'This is what is expected of me'. 'I'm supposed to' is most often used with the implication that you are not doing this (for example 'I'm supposed to be at work now, but in fact I'm stuck in a traffic jam' or 'You're supposed to give four weeks' notice when you leave your job, but in reality most people only give two.') In your example, the implication is that the student is unable to write the literature review and that he may try to get out of doing this. Perhaps he's going to ask his tutor if it's OK not to do it.

Yes, usually, but "have to" implies a stronger committment, or that things are out if your control. Eg You would say "I cant make it, because I have to go to class" but "I cant make it, because I am supposed to have dinner with a friend." The latter implies that you agreed to the dinner, and also that you might be able to get out of it. (PS, if you dont really want to go to dinner, but feel obliged, you would say "have to" -- "I cant make it, I have to go dinner with my ex-wife to talk about her problems.") PPS - Also use "have to" re something you must do eventually, but havent scheduled yet -- "I have to go to the dentist soon, because I am due for a checkup"

Yes, you can substitute it with 'have to' - 'I have to...'