Borderlands – Can you make a new Borderlands 2 character and leave off where your old character was

On the main menu, you will have a Select Character option. That lets you switch the active single player save. Once chosen, select Continue.

If you join another host's game, you can also choose which of these saves (characters) to play as in the first screen it shows you after you connect to the server, via the Select Character menu option.

Any progress in single or multiple is saved automatically per save. If you played co-op on the first save and progressed through the missions with others in co-op on their save (mission progression), any you complete with them will be saved on your character and you can't "go back" without creating a new character.

See How does mission progress work in multiplayer? for a description of how MP progress works when playing on other's hosts.

Doing some research as I was wondering this myself. . .

This forum post at Gamefaqs suggests that:

1. (Most?) legendaries can drop anywhere/from anything but
2. The chances in most places are extremely low and
3. Certain bosses/mobs have significantly higher chances to spawn certain legendaries. Does this apply to certain chests as well? I don't know.
4. It seems some legendaries only drop from certain bosses (e.g. conference call). Meant to come back and add this but forgot!

I am doing further research.