[CentOS] Unable to change runlevel at boot time

>
>    I have done changes as per James sir instructions but changes are not
> saving permanently.
>

Your first post described the steps to bout into a specific runlevel as a
one time thing with one error I corrected.

I suggest you rewind a moment and state clearly what your requirements are
- what are you trying to achieve?

If it is to change the default runlevel then amend /etc/inittab

If you want the removal of rhgb and quiet from the kernel arguments to
persist then amend the grub configuration in the system.