Like with all moves you do not have to use the full movement. It’s a movement potential ie. maximum. You do have to move at least 1 though, so no jumping in-place.
If there is more than one hero next to me, can I push the whole line or am I blocked because there is more than one?
Yes, you can push the whole line of heroes unless there is no wall, beam or gameboard edge that blocks the front of the row.
Can I drop things I’m carrying (maybe to have a free slot to steal from someone)? And if, can I do that any time during my turn or what are the limitations?
You can drop things at any time (including during movement) in order to make room for stealing. The general rule (in most scenarios) is that you can only carry 2 collectibles at a time.
I am a little confused about stealing… Can I steal a crystal before I move if the person is adjacent to me? And that I understand because I steal it and then run away with it. But say I run to someone and end up next to them. Then I steal a crystal from them. Does that mean before they move they simply steal it back from me? (In which case, what was the point of stealing from him?)
As the rulebook state on pg 8 (black box) you can steal from anyone adjacent at ANY point in your movement. So you can do both of what you described or even steal mid-move. Obviously running away after stealing is a advantage. If you dont have movement left over for this some abilities/cards (atleast one that i’ve seen but there may be more) also allows you to perform a extra dash after stealing (or use a DASH 1 potion in phase 3).
Can you tunnel/teleport to tiles which are occupied by other players/sheep/etc?
Yes. Your hero counts as having landed on top of them. See rules for jumping onto other heroes.
Rules state, the Movement ends after teleporting/using a tunnel. Is it allowed to teleport onto another teleporter or a tunnel and use that one in the same turn?
Yes. The teleporters act the same as board elements. Board elements must always be resolved before movement can officially “End”.
You need to “drop” all collectibles on nearest stable square. Are these items “pick-up-able” by anyone, perhaps in the explore mode? Or can they be “stolen” in the usual way, even though they are not in a player’s possession? If there is no way to recover these items, are they not effectively discarded, and shouldn’t they be removed from the board?
If something is sitting on the board it can be picked up as usual and is no longer considered as being held by any player.
When pushing other players/sheep from a diagonal movement, do they also move diagonally? what if pushing them diagonally against a wall/the board border? Is the push partially fulfilled (orthogonally), or not possible at all?
You push them in the direction of your movement. If they can not move in that direction, you can not push them. This may mean you can not move in that direction.
Does the natural tumble count toward my distance movement points?
It does not count toward your distance movement points. For example: you have 3 distance movement points. You do a natural tumble. You have then 3 distance movement points left for executing the skill visible from top after the natural tumble.
With Nim’s ability (wind that pushes all heroes 2 spaces in a random direction as determined by a roll of the direction die), how do I resolve a NW or SE or similar diagonal roll?
For diagonal directions that aren’t tumbled simply move directly diagonally.