need urgent help - H1 - extension - out of US after approval

[H1Canada]

Hi,

I am currently in US working with employer - ABC.

My employer applied for my H1 ext as it is expiring on end of Sept 2012.

after H1 approval, I want to go to Canada as my family moved to Canada temporary.

need urgent help to clarify following

1 - if I move to Canada and go on unpaid leave - for how many days my current employer ABC can hold my H1?

2 - Do ABC need to cancel my H1 as I am moving out of country

3 - if I get job with some other company in Canada (on Canada work permit) temporary then what happens to my H1 of ABC in USA.

4 - if ABC allows to work for me in Canada (on Canada work permit), for how many days they can hold my H1 so when I come back I can enter on H1

Appreciate your time