It's not really a Gaiden.. the "Number 1" and "Number 2" links you posted.
They're a special comic preview Arakawa made for the FMA game on playstation.
I'll translate it anyway.
Top frame: Chase after him, faster!
2 frames on middle left: *panting*
Frame on middle right: He ran inside the side alleys! Split up and give chase!
Bottom right: [Thought] If I've reached here, then...
Top frame, speech bubble on right: Stop doing that!
Top frame, speech bubble on left: You can't continue using the secret ways of <character name that I can't translate, sorry>
Upper middle frame, speech bubble on right: Let go! Don't disturb me!
Upper middle frame, speech bubble on left: I said no!
Lower middle frame, speech bubble on extreme right: It's finally solved! The reason for the destruction of <character/place/location name? that I can't translate>
Lower middle frame, speech bubble at middle: If you continue like this, you'll follow in the footsteps of <another character name> (Not very sure with this bubble, but I think I got it correct)
Lower middle frame, speech bubble at extreme left: Argh...
Bottom frame: What kind of a joke is this!
Sorry about the character and location names. I'm rather weak at translating Western-sounding names from it's Mandarin form.
the First one is for Broken Angel and then second one is for the 2nd FMA game for PS2. and also to the above Guest. their are more then one page to each one of those