Well, this is more like a Russian/petroff with the added moves Pc3 and Bb4. Normally white goes Nxe5 right away. Now it could go like this:
1. e4 e5 2. Nf3 Nf6 3. Nc3 Bb4 4. Nxe5 O-O 5. Be2 Re8 6. Nd3 Bxc3 7. dxc3 Nxe4 *
Looks a lot like it, but white does have doubled pawns. The 4 knights is anything with e4-e5 and the 4 knights out to c3/c6/f3/f6. Then it depends if white goes Bb5, Bc4 or d4. These quiet lines can all be found under the Ruy Lopez, the Italian and the Scottish game.
Think 3...Bb4 is a sound move, but maybe get a more active game after 3...Nc6 and if 4Bb5 Nd4
Yeah White can play 4.Nd5 Nc6 5.Nb4 Nb4 and wins the Bishop-pair in return for no concession(s) whatsoever. I used to play it as Black though occasionally it's OK but not great. Steinitz and other masters have played 3...g6 instead which is probably better for Black, I don't think it could be any worse than the dud line 3...Bb4.
Start looking in the game explorer here (it has several thousand games with this line) and start playing it and the 4 Kts until you get a clue as to which one you prefer (maybe neither once you learn them a bit) If you have a PC play these openings vs a chess program, hopefully one you can adjust it to play at about your level or slightly higher.
If you don't own any opening books consider MCO-15 and/or NCO (Nunn's Chess Openings) or at least a cheap used copy of MCO-14 and/or NCO from amazon or eBay.
GOOD LUCK!
In Sakaev's recent book on Petroff gives lines on both 3...Bb4 and 3...Nc6. In his best games book's see one or two games with Alekhine playing 3...Bb4. So don't think it such a bad line at all. 4Nd5 NxN 5pxN 0.0 certainly isn't anything to be worried about.
Thanks for all the info guys, I've just gotten a few alekhine games versus some recognizable players. Hopefully I'll learn something.
But oddly enough.. Black has a better chance of winning with the 3 knights than the 4 knights. On chessgames.com The stat's for the 4 knights is:
White wins 32.8%
Black wins 26.2%
Draws 41.0%
While the 3 Knights scores:
White wins 39.2%
Black wins 36.5%
Draws 24.3%
(That's a whooping 10% change!) Any black opening that scores only slightly behind in wins with a white opening is good. And by the reactions I've gotten playing it so far; people at my level aren't used to seeing a "ruy lopez" transposition.
Usually playing 3Nc3 in petrov is drawish line, unless your playing a lower rated player and you can outplay him, some time ago a player in a tournament played the petrov against me i chose another line than 3 Nc3, altough i admit it's not the only way to counter the petrov.
That's way like using stats too, only taking notice when supports what want to play anyway 
. Don't really see why black shouldn't be equal after either 3...Bb5 or 3...Nc6 though.
For those interested I've started a theme tournament with the Petrov Three Knights!
http://www.chess.com/tournament/petrov-three-knights-tournament
As far as the three knights opening, I don't know what to tell you about that. As far as your question on the four knights opening, I'd suggent that you look into the Halloween's Gambit. I like it, and black has to be very careful if they get back into the game at all.
Here my last and only experience with this:
www.chess.com/forum/view/game-analysis/petrov-three-knights-game
I found that at my level 4. d3 is one of the common responses by white, but then d5 equalizes right away and black has a nice game. Bc4 and Nd5 are the other most common moves for me. Definitely have had more success with Bb4 than Nc6. Very rarely see Nxe5 but have had good results against that as well and lots of white players manage to blunder their knight after a few moves xD
I'm looking for resources on this opening.. It goes like this.
Anyone familiar with this line? Also.. Do you know any thing about the four knights variation? I'm a little more familiar with that but i can't say I love it...