Hi hi yes!! Double card calling can be done with any two touching cards as long as one of the cards is still face down! So in the event you have just one card of your own face down, you can still double card call it with another card next to it that’s face up. Also, a card is only known if you’ve seen it with your own eyes, so any of the cards in the row closest to you or any card that’s face up; deductions don’t count! For example, in the instance where you can deduce what a card is with absolute certainty, you can use that information to intentionally make an incorrect call and give your opponent points :)
Hope that answers your questions! Thank you so much for playing!!