priiloader has been removed if you installed (or tried to install?) a new system menu.
if you don't have Bootmii installed as Boot2, you can't unbrick is without a hardware flasher
(if you have bootmii on boot2, remove the SD card, boot the wii and see the light. If it flashes 2 time quickly then you are saved! if not then your wii is bricked)
or maybe with a modchip (less hassle than soldering to NAND) and use a disc with autoboot flag (I think you need to edit the first byte of the ISO and burn it on a DVDR)
But you will need a console compatible with burned discs too.
There is also a "savemii" thing that I vaguely remember. something to do on a modded gamecube controller to trigger a hidden menu.
About CTGP:
no homebrew should require a specific system menu version.
When a program is loaded in memory (game, homebrew, etc.) the system menu is unloaded and not in memory anymore.
the system menu is like a homebrew itself, you launch it or not. it's only an application. none of it's files are used or needed by anything else.
if a homebrew tells you that you need 4.3, it's probably because you are missing a IOS (IOS58 maybe? IOS62?)
Or that you buned it as disc and tried to launch the game from system menu's disc channel without priiloader's antiupdate patch?
I don't know what you really did to trigger an update or requirement message..
Stub IOS are "IOS not used by nintendo anymore". You don't need to edit/change/delete them. just let them be there, they don't take any spaces on your NAND.
Following video ? ..... very very very bad choice.
NEVER EVER use youtube as tutorial or guide or help for hacking.
As on the forum, ask the developers, but never noob on youtube