[Dragon2]

if what Λ said didnt work try......

opening opera, in address bar type opera:config. press enter itll bring up a preference editor.......... scroll to install....... click it.........check the box next to browser first time launch........ now save....... now exit opera completely and restart opera again...............

now check and see if the default browser is opera, you may need to restart phone after that for it to work, but this has never failed me yet......