- No, it's not a process
- User threads are not rooted at init.
Init is just the first process, it does not manage any proceses or threads. It does create some, calling the kernel syscalls fork() and exec.
I think you have a muddy idea of what a process is. it doesn't just mean a bit of executing code. Yeah, the kernel executes before init (and the boot loader before that even).
But a 'process' has a specific definition of:
- Runs in user space
- Runs with a process ID
- Many interactions need to go through the kernel
- All resources need to come from kernel
- Needs to be scheduled by kernel
So, once the kernel initializes, it runs init, which then spawns whatever other processes it's configuration says to.
As far as #2 goes, all the kernel stuff is, well, in the kernel. Think of the kernel as a large area of code. Again, not a process, but a large code blob. Parts of the kernel deal with memory management, part of it with scheduling portions of itself (like drivers, etc) and parts of it deal with scheduling processes.