I can’t say exactly whether DoFs offer promises but my assumption is that yes they can, especially as agents can ask for them in the pre-negotiation-definitely-not-tapping-up-negotiation.
On the promise thing, no it won’t override the promise, the promise is separate and time bound. Unless you can make a new promise as part of that negotiation, but with outstanding promises, you may not get them to the negotiating table in the first place.