I came across something interesting on Synchrony's site and wondered if it really means what it kind of implies. Here's the blurb from their FAQ about how to shop online using your Synchrony Home CC:
It's the second paragraph that seems a little ambiguous to me. It could be interpreted as meaning this card is usable as a Discover card at any site. But is it?
Or are they simply saying that if you're on a Synchrony-accepting site AND they don't have the 'pay with Synchrony' option, THEN choose Discover as the card type and it will be accepted?
@simplynoir wrote:
'The Synchrony HOME Credit Card is issued and serviced by Synchrony Bank. The company is working with Discover® Global Network to provide greater merchant acceptance within the home category.'
Sounds like to me they're using the Discover payment network to process transactions. So in the event that just inputing the Synchrony HOME card number isn't enough selecting Discover as the card type should push the transaction through. This is assuming that the store/location accepts the Sychrony HOME card in the first place. Seems to be only through selected retailers which can be found on their website that the card can be used
Yeah, that's basically what I thought, but that second paragraph could be written better! 
Sync is using the Discover network to process payments from this specific card on websites that take Sync Home. Likely they worked out a deal with Discover to save on their processing fees vs Visa or Mastercard.
To answer your question more directly: No, I seriously doubt it can be used as a Discover card anywhere else - but it won't hurt to try it. Worst case it's declined.
So I went straight to the horse's mouth and asked Synchrony. As guessed above, no, it does not/cannot function as a Discover card in general. Its only use is at companies that accept the card itself, but don't recognize it when the number is entered, so they ask which type of card it is, then you specify Discover and it'll process. Case closed!