Is there an option to disable the whole text selection of input in Firefox when I change the application and return back. Example :
Notice that the search bar selects the whole text when I change to another Firefox screen and return.
Yes, this can be disabled. Access the advanced settings by typing about:config in the address bar. Then search for the setting browser.urlbar.clickSelectsAll. Double click this value to change it from the default setting of true to the "user set" setting of false and the URL bar will immediately stop selecting the entire text upon clicking.