Yes, it legally existed until 1833. However there were no large scale plantations in Canada, so there wasn't as much demand for slaves as there was in other British Colonies or the United States. Mostly they were household slaves and farm hands. One difference was that there was a larger influx of Native American slaves, instead of slaves that were abducted from Africa. It started to diminish around the 1800s but it didn't become illegal until Britain outlawed it.

Yes. Most slaves in Canada were Native people traded to the French by allied nations. There was actually a lot of demand for slaves in New France -- they could never get enough French people to settle there -- but because the things they were producing there were nowhere near as lucrative than the sugar and tobacco that was being grown by slaves in the Caribbean and American colonies, prices for African slaves were much too high for prospective buyers in French North America. Indeed, many indigenous slaves were traded from French North America to the Caribbean. As the other responder said, there were never any large-scale plantations in Canada (although French colonial officials were very interested in creating them, they were never able to) so slavery looked very different there than it did in other colonies.

A good book about slavery in New France, and where I got most of this information, is Bonds of Alliance by Brett Rushforth. You can read an excerpt here. You might also check out the story of Marie-Joseph Angelique, a black slave born in Portugal, who was hanged for burning down Montreal in 1734 (although it's not clear if she really did or if she was just a convenient scapegoat).

I have to say I don't know anything about slavery in Canada after the British took over -- Rushforth's thesis is basically that slavery was one of the ways by which the French embedded themselves within indigenous economies, and the British were not particularly interested in this sort of embedding, but as CodeNameZed said, it was indeed legal until 1833.