Unfortunately we don't stock Giant bikes so we cannot check the clamp size required but if you measure the seat tube diameter around your current clamping point you will have the right figure.
Judging by the specification I could find I would suggest a Top-Pull option.
""Top-pull" derailleurs are operated by a cable running down from above. This design is mainly used on mountain bikes, with the intent of avoiding running the cable under the bottom bracket, where it is exposed to spray kicked up by the front tire. " - Sheldon Brown