When the Runner installs Rabbit Hole, s/he can fail to find another copy of Rabbit Hole to install, either because s/he cannot afford to install the next one or because there are no more copies of Rabbit Hole in the stack.:Ruling The Runner should only shuffle the stack if s/he searches it.:Ruling
1. Can you use the search effect on Rabbit Hole even if you don't have the credits to pay for another copy of Rabbit Hole, doing so just to shuffle your stack?
3. Can you use the search effect on Rabbit Hole or Replicator even if the game state makes it clear that there are no more copies in your stack, doing so just to shuffle your stack? 1. Yes. You would fulfill as much of the effect as possible.
If I install Rabbit Hole and choose not to search my stack for another copy of Rabbit Hole, do I still shuffle my stack? I ask because the "Shuffle your stack" line in Rabbit Hole doesn't seem to be predicated on having searched my stack for another copy of Rabbit Hole - however, other cards that shuffle your stack seem to only do so if you've actually searched your stack for a card. You should only shuffle your stack if you actually use the ability to search your stack. If you do not, then nothing happens.