Please do not install AIsuite unless you desperately want to. And certainly do not have two monitoring applications open at the same time. Use HWmonitor or Coretemp.
1 Do all you overclocking in the BIOS, stay away from AISuite
2 XMP profile in mode of overclocking then the rest as per your plan
3 Do not bother with it now.
4 Your system freezes and you have to reboot.
5 Do not believe all you hear. Let temp be your guide.
I doubt that you will need more than 1.26 for 4.2GHz but no two CPU's are the same so it is impossible to predict what your system will need.
To help us help you - please provide as much information about your system and the problem as possible.