DuncanToys Imperial Yo-Yo, Beginner Yo-Yo with String, Steel Axle and Plastic Body, Green

Q: does it sleep ,if so how long

Depends on how tight the string is. The string is actually 1 long string that runs down and around the axial and then back up. It is twisted and different tricks will tighten or loosen it. When it is too loose it will not return at all. If it is too tight it will not sleep. your classic throw down and return tightens it 1/2 turn. A lunar loop loosens it 1/2 a turn.

Q: Does the yo yo already have string?

Yes, it does come with a string.

Q: Where do l buy string

It comes with string, but I wouldn't recommend these. Both our yo yo's never worked. They wouldn't wind up because the string was tied too loose on the yo yo.