Just find that I'm really struggling with surviveability. Anyone have any build tips?

Can someone explain how to unlock the new character if it says play Alpha Mode on Boss mode? I mean I did play Boss mode but the new character is still logged (it doesn't say if you have to win the whole boss level because it is impossible in any way to do that as the higher I got where the airship bosses). It has been almost a year that the new character was introduced :/...

found this precious gem of a game by Yippee Ki Yay Mr Falcon video on youtube, looked really fun

When I first time click it on the navy base mission to start it, as soon as I enter the game, the game itself aborted the mission (as soon as I click "play") without me doing anything and I had to restart the mission. https://steamcommunity.com/sharedfiles/filedetails/?id=3048201037...

I found a bug were if you hit the left bumper it say fatal error and then crashes. This only happens in the games combat I tested it on my ROG Ally and then on my desktop computer with an Xbox controller. Any help would be greatly appreciated.