Checking whether a creature has abilities for Jasmine Boreal of the Seven’s last ability happens only once each combat, as blockers are declared. This means that, once a creature you control with no abilities has been blocked, giving an ability to a creature blocking it won’t cause the creature you control to become unblocked.

Some effects give spells a player controls an ability. In that case, mana from Jasmine Boreal of the Seven’s mana ability can’t be spent to cast that spell, even if it is a creature spell that normally has no abilities.