A dog off leash

[ROBINDESBOIS]

A dog off leash
A dog off the leash
A dog off its leash

Which ones are correct?
How do we say the opposite a dog in leash?

[poli]

A dog off leash(perhaps in Britain)
A dog off the leash:good: a leash is better
A dog off its leash:good:

Which ones are correct?
How do we say the opposite a dog in leash?
A dog on a leach
A dog with its leach on.:good: