Is the Bluetooth 4.0(Ble) backwards compatible?
Who's device? Backwards compatible with what?
Is there one Bluetooth that will connect with all of them?
What is them?
Is it a programming problem or just hardware?
I'd say that almost certainly the answer is yes.
Where can i find a Bluetooth shield for the UNO that will connect with any existing Bluetooth's?
I think that expecting to find a bluetooth module that will connect with ANY other bluetooth module is a bit unrealistic.