Rook vs. Bishop: 4 Endings

In my own practice, I haven't seen many rook vs. bishop endings, and I suspect the same is true for many of you, too. Nevertheless, if we want to be well-rounded in our chess education, it's worth spending some time every now and then even on relatively uncommon endings, if they are fundamental. So here are four rook vs. bishop endgame positions; your mission, if you choose to accept it - and I hope you will - is to do your best to solve the positions before I present the solutions over the course of the next few days.

Position 1: White to move and ___, and how?



Position 2: White to move and win - how?



Position 3: White to move and win - how?



Position 4: Win or draw?