so the topic says it all.
Is that okay?
Depends on the booting phase, and when exactly you press the power off button.
Problems may occur if power is taken out while disk is written to, or something is not yet written to disk but is waiting to be written.
If you are in the grub menu and not yet selected any boot entry, then there should be now great danger in powering it off. But of course you’ll do it on your own risk!
What is the situation you are referring? For example, is keyboard non-functional?
i powered it off right after i logged in as root user in the tty, no display manager was running.
Also once I did when some apps were running like firefox etc.
Don’t do it, it’s too risky. Let it boot up then shut it down regularly.
In general, you should never use the power button to turn off your computer.
If you’re in the TTY, you can run:
shutdown now
If your computer freezes due to some hardware or software exception, do not power it off. Use the Magic SysRq button instead.
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You also posted this on IRC in #archlinux (and took up the time of three or four more people)… talk about duplicating effort. 
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NEVER long press your power button. This is called a hard shutdown and is only meant as a last resort. However, if you tap the power button while in a TTY or even in a desktop if that’s how you set it up, it can act as just a shortcut to the normal shutdown command.
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