A: Any player may look at the entire discard pile at any time, but the order of what’s in the pile should not be changed. So you can look at as many of those cards as you like, and if you see a card you want that’s, for example, third from the bottom, then (as long as you have at least three draws available on your turn) you can take all those “from the compost pile” to reach it.

In fact, when Composting is in play, some people choose to splay out the bottom of the discard pile to more easily see what’s within drawing range for a turn.