Overwintering plants

Does anyone know if you can keep chilean jasamine and corkscrew shell vine over the winter in a greenhouse? Do you cut them way back and how much water and what is the min. temp they can live with?

Mandevilla laxa is hardy to zone 8, so you won't have to worry too much about the temps, I'm assuming you're in zone 7? If so, even an unheated greenhouse would probably be enough to get it through the winter. And I think with the corkscrew vine (I'm assuming you mean Vigna caracalla?) I think you just need to make sure it doesn't get frost so you probably don't need to keep things super warm, just make sure it stays 35-ish or more, it's not like plumerias that'll be unhappy if temps get below 50. Can't help with your other questions though, mine live outside all year.