Right, just come back now (only for a minute, taking a break from other tasks). That recent picture looks like the "start up" dialogue after a factory reset, but I guess you've figured that out. You shouldn't need to worry about the RUU bit: that's only for really old phones, i.e. predating the HTC bootloader unlocking programme. If the phone is unlocked that bit wasn't needed.
Don't understand about the "fast double tap" problem (my instinct is to look at gesture and accessibility settings, but it seems an unlikely thing). Is this voice command thing a "Google Now" type feature, or some accessibility thing? I'm asking because I uninstall that type of stuff myself, so am not very familiar with it.
For rooting you won't find instructions on HTC's site. You'll need to install a custom recovery, then use that to flash a superuser package. There's
an XDA thread that claims to have detailed instructions for this model, though the fact that it recommends TWRP then talks about having installed "cyanogenmod recovery" is a touch odd (I think this is just an editing issue though - personally I'd also say use TWRP). It does include links to all of the files. I'd suggest reading a bit of the thread, at least first few posts and the most recent, in case there are reports of problems, but to me this looks like what you need.
