No, any command that is not white listed in the official rules forum post are not allowed. You are allowed to manually change to a more preferable FOV in the settings menu before your run, but changing it using a key bind during/ before a run is not allowed (I'm pretty sure), since it is not white listed . What i'm not sure about is why you would want to have a key bind to change FOV in the first place, but to each their own I guess :)
default_fov is cheat-protected fov isn't cheat-protected
Obviously any cheat-protected command is banned, therefore, it's banned.
I believe there is a slider for fov in the advanced tab in the settings menu, I'm not at my computer right now so I can't check
It was recently discovered that it is possible to set your mouse sensitivity to a value so high that the game considers it infinite, leading to several new glitchy techniques being discovered.
The rules have now been amended to ban these new techniques in both Inbounds No SLA Legacy and Glitchless.
