Well, I'm not sure there is one for Red, but get Blue rescue team, there are more codes for that.
You can find it on any floor in any dungeon.
the 99th floor
Floor 6 on the 7th dungeon
i think floor 30 or 45
No I don't think so.
Mewtwo is on the 99th floor of western cave
Mt Faraway 40F
In Pokemon Mystery Dungeon: Red Rescue Team Latias is found after you complete the 25th floor of Pitfall valley.
In any floor i found it on floor 2
Silver Trench I think 40th floor
The 50th floor. you can also get it from medicam
Celebi joins your team in Purity Forest on the 99 floor.