Can two apps in one iPhone can be connected to same peripheral?
The Bluetooth connection is established between the phone and the device - the device does not exclusively connect to an individual application. 

To answer the question a Bluetooth device can be used with multiple apps that are designed to work with it. For example, a Bluetooth speaker works with the Music app, it also works with YouTube etc. 

Your device may have limitations that I am not aware of but without more information I can only tell you know Bluetooth works