I have seen expansions of many English words such as POLICE, MUSIC, GOD, LASER, where each letter supposedly stands for another word, as in an acronym. Are these expansions in any way real, that is, written in a standard dictionary, or are they just made up?
Police is not an acronym or abbreviation, normally. You could make a backronym for it if you wanted.
In general, any word older than the 1950s is pretty much guaranteed not to be derived from an acronym. There are exceptions, but if someone tells you a word is really an acronym, just disbelieve until you've checked a reputable reference.
The word laser was originally an acronym, which stood for:
According to the Oxford on-line dictionary entry for laser, this originated in the 1960s.
However, through common usage, the word laser has been adopted in its own right and is defined as:
There are other examples of acronyms that have been adopted into the English language as words in their own right:
RADAR - RAdio Detection And Ranging - defined as:
SCUBA - Self-Contained Underwater Breathing Apparatus - defined as:
Some other examples: