Premiere Elements (any versions) does not offer project presets with frame rate greater than 59.49/60 frames per second nor export settings with frame rate greater than 59.94/60 frames per second.
You can create slow or fast motion effects in Premiere Elements 11 through 14
Project Assets/ Right click of video thumbnail, Interpret Footage and its Frame Rate section
Time Stretch and its Time Stretch dialog Speed % and duration
Time Remapping (Tools Menu/Time Remapping)
what program does support 120fps rendering?
I do not know of any program(s) that supports 120 fps rendering, not even Premiere Pro which I do not work with.
The following is a link to a 2013 Premiere Pro thread discussion on this matter. It may be of interest.
You could post in the Adobe Premiere Pro Forum to get an up to date opinion on the matter.
Have you contacted GoPro support? It should have the up to the minute information on this.