It's a really simple process to move from the default A pose to a T pose. You just have to bring the legs together more (the side-side on the thigh bones) and raise the shoulders. I don't have the exact values memorized off the top of my head unfortunately.
That won't give a G9 figure a t-pose gaver. It will just bring it back to the G9 default pose, the a-pose. Apart from a very few reasons I can't see why you would want to put G9 into a t-pose anyway.