Iron bundle's Hyper blower ability against single Pokémon

[Slytheryggy]

Iron Bundle's Hyper blower ability reads "Once during your turn, if this Pokémon is on your Bench, you may switch out your opponent’s Active Pokémon to the Bench. (Your opponent chooses the new Active Pokémon.) If you do, discard this Pokémon and all attached cards."

Your opponent can't choose as the new active Pokémon the one that was switched out to the bench, right?
And what if they had only their active and no other Pokémon in their bench, can I still activate Hyper blower? (as a way to free a bench spot, for example)

 

[PokePop]

No. It is "switch" so it cant be the same card.
No, you can't use an Ability if it has no known target/effect. In this case, it can't push the Pokemon back, so it can't be used.