Can I swim with a lisfranc fracture?

You should not. This really depends on how long you have had the fracture and how displaced it is, and how you have been treating it since the injury. If you are waiting for it to heal without surgery, you should not be bearing weight on that foot at all. This would include getting in and out of a pool and using your foot to kick in the pool.
Depends. If it is stable and does not need surgery, i would let my patients swim at 4-6 weeks post injury.