i want to know the technical differences between distros? Red Hat's network configuration files are in different directory than of Ubuntu, what controls this differences?

When booting any distro what are all files required?

After POST boot loader gets control and passes it to the default or selected kernel and loads kernel image and initrd images and then init process starts loading all services, is this the sequence of booting for all distros? After loading all services a login prompt is provided, when log in to the server the associated shell with the account opens and wait for commands.

So There is KERNEL > INIT > SHELL right then basically what is the difference?

Well for starters, they're using different versions of the kernel, probably with some custom distro-specific patches. Then they use two different init systems; RedHat (if I'm not mistaken) uses SysV init and Ubuntu uses Upstart. Other distros might use systemd, or just a shell script.