As your flight has be retimed by 4 hours, I would expect you to be able to rebook (for free) to the following day without any issue if you call TK and explain that you can't accept the retimed flight and wan't get rebooked to the later. You don't pay change fee and fare difference because your rebooking is considered involuntary because of the schedule change of your original flight.

How to deal with your upgrade based on an E+ voucher I don't know.