Hadn't seen this one yet, just the one of her fighting the Kree. Many thanks for providing a better look!
Costume looks as great as I could have hoped for. Very, very happy with this design, and I hope the final version sticks close to this (with the sash added on for no reason other than its fun).
As for where Carol has been, if she's dealing with the Kree and the Skrulls, it'd be easy enough to say she's been in space this whole time trying to steer the war away from earth, or possibly even end it completely.
We don't know anything about how the Nova Corps and the Kree came to a peace treaty after centuries of war, perhaps Carol negotiated it? Something like that would certainly provide some weight to the "most powerful" moniker Fiege keeps tossing around. And if she's that powerful, she might not age at the same rate as a normal person so the time lapse wouldn't be an issue either.