Demos are very simple to install. You must not use YarisSwap, because it's only for RGH. If you want to install them, use Horizon (https://www.wemod.com/)
You can also inject demos in to USB flash drives with USB Xtaf: How To Inject Xbox 360 Content Using Usb Xtaf v45 which is what i usually do.
Yes, but Horizon is better for begineers. If you are advanced you can use the usb xtaf of normal windows Explorer Edit: I think i saw you somewhere someboy101. Wasn't it on WinWorldPC? I cannot remember