Directly in the player. Open up any episode and look for the extension logo.
Hover over the setting's text to get a description.
Your browser is most likely restricting that feature. Here's how to fix it:
Chrome does not restrict autoplay, but may restrict sound playback.
Opera does not restrict autoplay, but may restrict sound playback.
No, and there are no plans to implement it because different ad providers use different layouts. If that's a problem, use ad-blocking extensions.
No. Even though it would be interesting to have broader coverage, there are no plans for it. You can try forking and experimenting.