like can Montreal trade a 2030 1st for Laine for example?

Don't know the official answer, but Gretzky was traded in 1988 for (among other things) picks in '89, '90, and '93 so that is 1, 2, and 5 drafts out but that was many CBAs ago.

Maximum offer sheet compensation spans 4 consecutive drafts, so at least 4 is likely to be allowed. Even if you could trade even more distant futures, I doubt GMs would be interested in that given the uncertainty that surrounds team results 4+ years forward (where the pick would be within a round) and the difficulty of judging the depth of a draft class when the members might be 13 years or younger when you make a trade.

There is no limit to how far in the future draft picks can be traded. Theoretically you could trade a 2121 pick if you wanted to. However, that would be silly, and draft picks are usually traded a maximum of 4 years before a draft.