What are the multiple interfaces that you are trying to create? If the interface class is FFh, then it indicates that it is a vendor interface and the sub class field becomes irrelevant.
You can always create a separate interface having only the control EP if you wish .
I am trying to create a device which have data path and control path. I created a composite device with two interfaces with 0xFF classes and it worked fine on windows 7 but not windows 10.
What do mean by I can create a separate interface having only the control EP (does this meaning without any in or out endpoint)? I can post an example descriptor that would great.
Yes, you can create an interface only using a Control Endpoint and no other endpoints. Just put the no of endpoints in the interface descriptor as zero. Doing this will allow you to use only the default control pipe.