When an alarm is supposed to trigger does it do anything at all on the screen?
try this
1 Google search should not be your 1 choice for troubleshooting.
Yes googl is cool enough and you can always find somebody writing about something about what you search for thus world wide web.
2 about the alarm problem, alarm will always work if in sleep mode, if in flight mode or if in Blocking mode..
3 Test your alarm set an alarm for like in 3 min check if it rings and be sure you selected the appropiated days for it to ring else it will only ring on those days you selected..
* 1 Clock
* Create Alarm
* Set Clock to ring
below tap days
M T W T F S S they will change to green.
(This option because you can have multiple alarms for diff topic's)
* Alarm Type below days, tap to set type of Alarm
(Melody, Vibration, Both or orientation) Choose Melody for sound music what ever you want as choice
* Alarm tone below Alarm Type, tap to set a specific tone tap one to test it is also really a sound you can actually hear, that it works.
Press SAVE give it a name for the occasion
When an Alarm is active alarm clock icon will be added to the left of the signal type of your carrier.
See example:
http://cdn.webcazine.com/wp-content/uploads/2013/07/create_alarm_20130709.jpg?00d8d4
Note you can activate deactivate the set alarm in the Alarm menu by tapping to the right of the Alarm Name, Standard (Alarm) active is green / deactivate it turns white + icon notification area upper part of screen disappears..
Yes if any process killer is running check the list, but it shouldn't deactivate the alarm process only if Clock app has been deactivated but then is not visible at all in Programs..