What youtube video told you that? There is so much incorrect information on youtube created by clueless people claiming to be experts in order to harvest links.
The SX60 is one of the newer DIGIC6 cameras and booting from this cameras via the "firmware update" method (using a ps.fi2 file) is unreliable. You should really use the "SD Card Lock" method.
However, if the C version actually has a
ps.fi2 file then it will be possible to build one for your G version - but you don't have to wait for someone to do that if you use the other method.
Also, you can't change the firmware version of a Powershot unless Canon issues one of its very rare updates. And you certainly can't go to an earlier version.
Complete details about installing CHDK can be found here :
CHDK Wiki : Prepare Your SD CardI very strongly recommend using either the
STICK or
CHIMP utilities linked at the top of that page.