I went to the website of "Classic Shell", and under the topic FAQ's, they specifically state that it will not run on Windows 8.1 RT.
Also, I emailed the author of "startisback", and asked the same question regarding his program running on Win 8.1 RT. I just received the reply; Will NOT run on Win RT.
Win RT apparently is a totally separate kind of application from Win 8.0, and Win 8.1 Why MicroSoft would make such a program is anybody's guess. Windows 8.1 RT is the program on the MicroSoft "Surface" family of tablet computers. Mine is a Surface-2, and is certainly a nice tablet with a superb touch screen, and full size USB 3.0 port, memory chip port, sound port, HDMI port.
If I knew this incompatibility issue, I would not have purchased it. The MS "Start" package that you must work thru seems to be designed for social networks, and sending/receiving pics and music. They call the different applications "Charms" and in the several hours I have tried to use make sense of it, has been a totally "maddening" experience.
It almost seems to be more of a "psychological experiment", than a usable computer.
John