Re: Flat footed stance
Arm punching is when you don't rotate your body into the punch, though the power should come all the way up from your feet, you're still not arm punching if you use your body (though big george did seem to be able to nearly kill people with arm punches)
Flat-footed fighters can still pivot the rear foot to throw a right, though it's unusual to see them pivoting the left to throw a hook.
Think of what you do and how it feels when you step into your punch. That's essentially what you do when you fight flat-footed.
You sacrifice power for mobility, you aren't able to change angles with your footwork when you throw. This is why you often see flat-footed fighters following fighters in straight lines - because their footwork doesn't allow for them to pivot and punch or to move laterally very well.
It's not always sluggers though - someone like Cotto will move on his toes, plant his feet and throw and then move again. Others, like Maidana, are flat-foted throughout the fight, he seems to load up on every single shot with the intention of doing as much damage as possible