Harmful if often turn on / off (restart) iPhone?

No, it's not harmful. Apple wouldn't have provided a button to turn the phone off it it was.

I think they this person means a hard reset..

This is an interesting question, because to be honest it's a yes / no answer. In all honesty it depends what you're doing but it's always best to not have to hard restart the device.

MacKing wrote:

I think they this person means a hard reset..

This is an interesting question, because to be honest it's a yes / no answer. In all honesty it depends what you're doing but it's always best to not have to hard restart the device.

No, that will not hurt the phone, either. If it did, Apple wouldn't recommend it as a troubleshooting step.

MacKing wrote:

I think they this person means a hard reset..

This is an interesting question, because to be honest it's a yes / no answer. In all honesty it depends what you're doing but it's always best to not have to hard restart the device.

You are incorrect.