can I flash a stock rom onto a working stock rom (factory reset is not working)

[wilfrat]

if i flash a stock rom onto a stock rom will it break or will it delete the old and work fine i need to know because my factory rest doesent work and none of my google apps work

pls help ive been battling with google apps for about 3 months and still cant fix it

 

[Rukbat]

It just replaces any existing ROM (remember to clear the cache [in recovery] after you flash it).