Yes, there is a full range of current NowTV devices available for purchase on the NowTV website.
Or from Curry’s or from Argos.
Though only the white boxes are truly superseded; even the old black ones remain fully updateable with the full range of NowTV features.
Sure you will.
The offer on the new device will go and live at the top of My Account/Passes & Vouchers, ready to be redeemed by you in the last month of your existing offer, to continue on from it.