you only have to do a short sidequest to get the sabrecat, but would you really want to walk through argonia? *shudders*

plus its a kitty! he cant be called anywhere though, like in empycchu...okay, you probably arent that far yet, nevermind

yes, but like the above post said, flying is only for getting through some parts of the story, and reaching places that you couldnt get to without it. (if there are thick white clouds, then its a place reachable only by flying.)