All that's possible in theory. Not sure why there's been this big thing about this latest 'flextension', as it's inherent in A50 that if we agree a deal before the extension end date we could leave early. A referendum can't be forced though, just as Johnson has found out he couldn't force Brexit if there isn't a majority for it in Parliament. Legislation needs to passed before it can happen. As for what such a ref should ask, would've thought one of the deals the EU has agreed to v Remain... ETA: If in an election the Brexit Party advocating No Deal won more votes then the Tories advocating Johnson's deal, then there's a good argument to say that No Deal should be on the ref ballot paper instead