Logitech Unifying devices don't actually use standard Bluetooth. It's a proprietary 2.4 GHz signal similar to Bluetooth, but it's only going to work with a Unifying receiver.

Is Unifying receiver better than Bluetooth?

Is Logitech Unifying Receiver Better than Bluetooth? Neither technology is better than the other. Unifying technology is also based on the use of the 2.4 GHz frequency range, and the technical specifications hardly differ from Bluetooth.

How do I switch from Bluetooth to Unifying receiver?

no you cannot seamlessly switch between Unifying Receiver Mode and Bluetooth mode. After you have paired the device in bluetooth mode, it remains in bluetooth mode until you turn it off. when you turn it back on again, it is in Unifying Receiver mode until you pair it again.