Excellent distinction, Proxima! ;) I included tutorial levels for both (2) and (3) in Lemmings World Tour, without actually having thought about the difference. Although I did outline some tricks, like the double-builder turnaround or the miner-cancel turnaround, as more obscure than others. Lateral thinking, in contrast, can theoretically be inferred, although it usually also requires at least on example level to get the player used to thinking in such patterns, therefore recognising them whenever they appear in a level.
My example of "tunnel turnarounds" was a level by Nessy...
..."Ancient Temple of Lemming". Even though I had discovered the tunnel turnaround trick before all by myself, on the original ONML level "Method in the madness", I did not actively look for opportunities yet to exploit this. Possibly because the "tunnel" in said ONML level is very short, so you only have a very tight time window where you can do this. That makes it seem like more of a one-of trick, rather than something you can make use of in general.