IME, "aiki" has a very specific definition in aikijujutsu. But, because transmission has been spotty, incomplete, and, in some cases, cross-pollinated with practices from other arts, it's pretty hard to nail down a universal definition that permits everyone to speak from the same perspective.
That said, aiki as I know it (from two separate lines of aikijujutsu and from one Chinese internal martial art) is the intent-driven manipulation of a body state that we create and manage. Therefore, when you move with an "aiki body," it will manifest itself in everything you do, whether kata, applied technique, or free-form "street" combat. It remains, then, for the individual to develop the skills -- formal/kata, waza, combat -- so that that they will be able to serve as sound vehicles for the aiki engine that will drive them.
In my experience, 1 and 2 are the same, because the techniques of Aikido are abstractions of the kata of Daito ryu, of which some were designed to teach you how to create aiki. (YMMV).
But 3 is the only situation where aiki is "true" aiki - and it probably still isn't quite unless you are one with the universe and all that.
This is because Saotome Sensei's inspiration comes from Osensei's later years when he was, apparently, doing little but walking into the dojo and manifesting aiki in a free-flowing, dynamic way.
I think the 3-level Saito Sensei paradigm was an attempt to realize some way to bridge the gap between lower-level practical learning and the more lofty, metaphysical applications Ueshiba had gotten into while living in Iwama.