The metagross-looking thing next to Tokyo Tower is a Huge, one of the monsters they fight in Assault Lily. (Specifically, it's the one from episode 1 of Assault Lily Bouquet.)
For comparison, their canon weapons are Toriko normally uses an AK-101 and Sorawo normally carries a Makarov pistol she got from Toriko. The AK-101 was acquired in the other side. They are the weapons most commonly depicted with them in cover art.
It doesn't imply that since this is just how volume 1 played out, minus all the blood.
It's likely based on the season 2 episode where Aqua imagines this specific scenario in order to properly guide his acting through emotions rather than calculted gestures or imitation of other performances.
That definitely seems to be an error, but there apparently have been cases of curved FAL mags existing, and apparently some guy filed down a Bren .308 mag to fit in the magwell of the FAL, to great success.
