Provided it's recognizable as the original story, you can certainly retell it from the antagonist's perspective similar to Maleficent. Changing names or the order of events is also acceptable, especially if this is a legend, fable or fairytale we're talking about-- they've been around for hundreds of years, people have changed them due to faulty memories, personal preferences, and their own opinions.

The weird question is also an interesting question... I'd prefer if species-changes had some sort of purpose in-story, but I wouldn't really object strongly?