Welcome, there are many spells on this website that work and many that don't.
You can be certain though that any spell claiming to physically morph your body in any way is false. Magic cannot change your DNA or how you look; anyone claiming to be a mythical creature or anyone claiming to have been able to change their body is more than likely lying to you.
Also, just because a spell is said to be guaranteed to work doesn't mean that it will one hundred percent work for you too. People write spells to fit their needs and their way of practice and spellcasting, so it's possible it won't work for you or it may not work in the way you were expecting.
I recommend before trying any spells to study spellcasting and master the basics of magic (i.e meditation, visualization, grounding). By doing this you can gain a much better understanding and not only give a better guarantee to your success in casting, but you can also find the path that is most suited for you.
I suggest reading the links that came in your mail, they are very helpful and they can give you a basic understanding of the kind of path you will be leading when practicing magic. Magic is a wonderful thing and the community here is helpful and kind. I hope you feel at home with us!