Etemon can be found in the Doomsday Forest.

What level is Etemon?

Etemon is a ape-like ultimate-level virus Digimon that is the second primary antagonist in the first season of Digimon.

How do I recruit Biyomon?

You need to progress through the main story quests until you have to head to the volcano area. There you will encounter a Birdramon, he joins your city after you defeat him in battle. Speak to Biyomon after Birdramon joins the city and she will join also.