This article refers to Digimon World 3.
 Can I get (insert digimon)?
All the playable Digimon are listed on the game page. If it isn't in there, you cannot control it. For quick reference, though, anything you can meet in a random battle or tamer battle is not playable. A select few bosses are.
 The game ends after I clear Gunslinger! Why isn't it continuing on?
You've got the US version of the game. The Japanese and European versions continue after beating Gunslinger. The US version doesn't.
 How can I get more Rookie Digimon?
Acquiring a new Rookie Digimon involves speaking to the Rookie Digimon's DRI Agent, meeting certain level criteria, acquiring the necessary DDNA from the Rookie Digimon's Ultimate form and returning to the DRI Agent. The DRI Agents page explains the process thoroughly, and contains charts to show how to get each Rookie Digimon.
 What's the password in the Admin Centre?
In Asuka Server, it's "MONSTER". In Amaterasu, it's "DIGITAL". (as in "Digital Monster")
 Where are Nick and Keith at?
When asked by Lisa to get Nick and Keith, they're in the lake behind Suzaku City. To get there, go through the leader's room and dive at the docks, then follow the flooded tunnel until you reach it.