This is now possible in Windows Phone 8.1, as the Volume Bar now has an interactive slider for ringer volume and a separate toggle for vibrate:
To open the Volume Bar, press either of the volume keys as usual, then expand it by tapping the chevron. Reduce ringer volume to 0 with the volume keys or by dragging the slider, and now you can toggle between ...
A feature called "Quiet Hours" has been introduced into the core operating system with the 8.1 update. You can trigger quiet hours manually, or automatically with a preset time (e.g. via a calendar event). A cool feature related to quiet hours is the concept of an "Inner Circle". This is a group of contacts, e.g. your significant other, who may contact you ...
The volume will always revert to a default level after a restart. This isn't a bug but a so called "safety feature" to prevent hearing damage if we should accidentally forget to lower the volume when listening to music through a headset/ear buds.
It's in the tutorial somewhere but can't find it now.
From Windows Phone Help:
Alarm volume is separate from the overall phone volume and can't be
changed. As long as your phone is on, your alarms will still ring out
nice and loud even if you turn down or silence the phone volume.
The above applies to any Windows Phone out there. I used to have an LG Optimus too and I can't remember being allowed to set ...
Do not reset your phone! This warning will ALWAYS show up as far as I'm aware. It seems to not happen so often anymore after the WP8.1 update. Also, if you do not restart your phone very often, it should not happen as much. It seems to just happen a few times after startup.
Since you mentioned it works fine when you remove the headset, try replacing the headset with another. Your phone has support for headsets that have volume controls on them. If your headphones are not seated correctly, they could be triggering the signal for the volume.
If this still persists with another headset, take a flashlight and look down the headset ...
There are some songs in my library too which are not responding to the volume command, but not all. I think this is a bug related to nokia music because 99% of those songs are from nokia music. I think you should cut that song to your computer and paste it back. Otherwise you should simply delete that song and download it from some other source.