ADDITIONAL INFORMATION: Yes I have played Fallout 3, I played it and beat the main story line then stopped since I didn't have any downloadable content and the game just ended. Don't hate on me for not knowing these things.

Where do I find a dog to be my companion?

Can I have multiple companions at once?

Do I need to complete every quest to go back to the vault and talk to the girl again and do that quest?

What is the Max level?

Are there any mods that raise the max level?

More questions might be added in the future.

1. You find the dog companion at the Scrapyard

2. Yes, you can have two at once, but only if the second companion is the dog.

3. You just need to have completed the "Waters of Life" quest, to get the "Trouble on the Homefront" quest.

4. The max level is 20, 30 with the add-on "Broken Steel".

5. I'm sure there are several mods the raise the max level.

Hope you got the answers you wanted.

1. The scrapyard, located near the Wheaton Armory in the western half of the map.

2. Not in the original game, but you can with mods.

3. No, you just need to complete scientific pursuits. Go back to Vault 101 after that quest and Amata should be sending out a distress signal, look for it in your pip boy's radio.

4. 30 with Broken Steel, 20 in the default game, and yes, it can be increased with mods (I wouldn't recommend this however, I find that your character is plenty overpowered at level 30).

I would suggest exploring the game, there are a lot of cool secrets to be found in Fallout 3 by simply exploring the world. The main quest is not by far the biggest part of the game.

You can get two followers on console. Just sayin. The max level, imo, should be 20. You won't need levels past 30.

1, 3, 4 What they said.

2. Two companions as long as one is the dog. More if you add mods. I currently travel with 4 companions.

5. There are at least two mods that raise the level, Level 50 Mod and Level 100 Mod.

While mods have been mentioned, there is a mod to allow you to continue the game after you have completed the main quest without having any of the DLC.