

Developer : Retrific Genre : Multidirectional shoot 'em up Features : Local Cooperative Gameplay Local 2-player Release Info : Xbox Game Pass Achievements : trueachievements.com

Jim and Flint can be unlocked by taming a wild dog. It's a neutral NPC spawned in the first 3 levels. It looks like the hostile guard dogs, but it's neutral. You can play fetch with a Stick to get it as a companion.
The Colt Canyon Fandom wiki has weapon stats. To defeat the bosses, the Sustained Damage per Second (SDPS) seems relevant. Now, how to get the Auto Shotgun?
This list on the wiki shows the unlock conditions for all weapons.