Disregard, figured it out.
The first three are pretty easy in terms of epsilon-delta, if you really want to go that way. (d) isn't. You need to know pi is irrational and what that implies about the integers mod pi. Though it is sort of clear 'intuitively'. This makes me think the question is more about understanding what lim inf and lim sup are, rather than about proving what they are. And I think you do understand that.
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