Does the metamagic feat Focused Spell work with Aqeous Orb?
As Shiroi said, "Theoretically" it could based on wording, but I think is not intended. Note that the aqueous orb has effect targeting, so it doesn't target creatures directly... but can affect them in case it's cast in their square. This way you could consider it "affects" creatures.
Still, note that Focused spell also has a rule that makes it only work if more than one creature is affected:
When casting a spell that affects or targets more than one creature
That means, you must make it "catch" more than one creature when cast.
Since it's a metamagic feat and generally those get applied before the spell is cast then it's limits must be based on the spell description not a particular senario.
So, it only works for spells that have:
1. Specifies 1 or more creatures as their Area or Target.
2. Allows a saving throw
Once, the feat has been applied, you can cast the spell and if its only able to target one creature you can select that creature to be the one the focused spell applies to. The feat is limiting what spells you can apply it to, the only limit when you cast it is that you have to specifically target a single creature that is included as part of the group of creatures you've targeted, at the time you cast the spell.
If for some reason, the spell lets you target additional enemies on subsequent rounds after it's been cast, the creature you initially selected will continue to be the target of the feat and that choice can't be altered for that spell.
TLDR: No, aqueous orb is not a valid option for the feat.