I found out a thing that I'd like to share.

[hisham691]

I found out that the key combination for soft reset is not volume down + power button .. Just press and hold the power button for like 10 seconds and that's it.

 

[AndyCalling]

That is not the same as a soft reset. That is just a 'reboot' just like switching off and on again but with one press. I got confused by this as well, but you'll see the time/date reset then correct with a proper soft reset, and you won't with a simple reboot.

 

[hisham691]

Thanks for making things clear

 

[Guytronic]

Just press and hold the power button for like 10 seconds and that's it.

Some Lumias seem to have a one button soft boot feature.
I have a T-Mobile 635 here (under W10 currently)
I've always rebooted this phone by holding the screen off button for about 8-10 seconds.

If I hold the button then swipe down to shut off the phone off I see the "Goodbye" followed by the calendar reminder (W10 only) phone then stays off.

If I hold the V- and power button together I get the slide down for off.
Continuing for 10 seconds or so the screen blacks out phone vibrates and restarts.
If I hold the power button alone the slider shows up.
Continuing to press for 8 seconds the screen blacks out then vibrates and restarts.
This was the same under W8.1 Cyan.

When I first got this phone there was in the Lumia help and tips app a listing of one button "soft" reset devices.
I'm unable to find this information since the app has been changed.

 

[AndyCalling]

The L930 does this too. It is not the same type of soft reset as the vol down version though. Odd, granted, but the 930 does respond differently to each version.