question about perm and I140

If I apply PERM now, how long will it take to get it approved?
Once I get perm approved, can I apply for I140 immediately? and how long will it take to get I140 approved?
Since my current H1B visa is using year by year extension after 6yrs, Can I apply for H1B visa extension just based on I140 approve, or I have to use previouse LC pending to do H1B extension?

Really appreciate for your help!