Used according to manufacturer's recommendations.
No.
Yes.
It has been found to be slightly effective in marine tanks in making proteins more easy to skim out of the water, which is basically irrelevant.
You could ignore the manufacturer's recommendations, remove the UV lamp from its housing and wave it over the algae. This however would result in severe burns, blindness, cataracts, tumors and death.
Of the available options I suggest spending the cost of the UV steriliser on bourbon and coke to be taken orally while looking at the tank and not giving a crap about a little bit of algae.