This is an old thread, so it would’ve been better to ask this somewhere else.
I think you would know most of this if you had the dungeon unlocked, so first something about the dungeon:
The dungeon can be found to the left of the merchant, and unlocks at team level 35. When you open it, you can see 3 gamemodes, of which only Endless is unlocked by default. Next to the dungeon title there is an “I” for more information, which answers your last question.
As you walk through the dungeon, you can encounter traps or trapped chests. There’s a chance to disarm them, but if you fail to, you get a debuff, such as: “A random skill on one of your heroes will be disabled” or “in the next fight your heroes will be stunned for 4 seconds”.
On the main dungeon screen (where you choose one of the three dungeons) you can choose to reset the dungeon below the “Enter the dungeon” button. This revives all your heroes, and resets your progress to floor 1.
Farming isn’t a term in the dungeon. I don’t know where you got that. You can earn gear, XP and influence in chests in chests in the dungeon though.
Reading the first post in this thread and reading the dungeon instructions I referred to will answer most of your questions.