1. Not yet, or planned at the moment.
2. In the skyspec.txt file try changing these numbers. This rotates the sky. Skyboxes are still a work in progress.
;SUNLIGHT DIRECTION VECTOR
SunDirection = 100,100,100
3. Not sure when the new public preview will be out. There is shader work still being done on it.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit, Screen resolution 1680 x 1050.