

This assumes you have a machine which supports proper S3 sleep, which newer devices increasingly do not :(
A lot of modern laptops only support S0 “modern standby”, which basically means the kernel puts all processes including itself on pause, but the CPU and all other components are still powered despite being idle.
Not sure what you’re trying to ask, are you asking if using sudo to sign in as a different user will make kernel updates take effect? If so, the answer is no.
Linux is an operating system kernel, which basically means it’s a program which runs other programs inside of it. For any “normal” program running inside Linux, you can update it by installing the new version and then exiting and relaunching the program so that the installed updates take effect. Similarly, after installing the Linux kernel itself, you have to exit and restart the kernel in order for the update to take effect. Because the kernel runs programs inside of it, exiting the kernel means all of those programs will be exited as well, and because the kernel is the only program running directly on the hardware, exiting the kernel means that your computer will power off. In simpler terms: getting kernel updates to take effect necessarily means you need to exit the old kernel and launch the new one, and there is no way to do that without reboot.