Unless somethings changed recently, no you can’t.
Can't remember the game, but we actually had a free kick given against us in our own half for offside quite recently at the Amex.
I think this was down to blind, rank steaming incompetence on behalf of the officials though, as opposed to an actual rulechange.
Er yes you can. As discussed previously on here for a recent home game. If the player runs from an offside position back into his own half towards the ball he is deemed "active" and is given offside in his own half. You couldnt make it up it is so stupid. It changed under the new active ruling to the law.