With that angle of view aren't you forced to extend your arm or use a tripod to take photographs to avoid including your feet in the picture?
No, that is not an issue at all even shooting in diagonal mode (where the angle of view is the widest).
In case the camera is held at level at 1.8m (100 times half of 36mm frame width) from the ground in portrait mode, there is still 1m (100 times the focal length) "free" in front of the (zero length) feet.
The novelty of this Samyang lens is that it is the first FF 10mm lens for DSLR's. Cosina already sells a FF 10mm lens (called Voigtlander Heliar-hyper wide 10mm F5.6 aspherical) for mirrorless cameras in both Sony E-mount and Leica M-mount versions.