So is it "hører på", but "lytter til"?
Why is it not "radioen" for "the radio"?
How would you say : one hears it on the radio ( when there is an earthquake)
There are barely ever any earthquakes in Norway, and most are too small to notice, but I guess something like "Man/En hører (om) det på radioen".
Kan man også lyssne på radio?
How can I distinguish between the pronunciations of MAN and MANN?
you can't, they sound equal. But you can distinguish them from the context, since mann almost never can be found without article (mannen or en mann).
What's the difference between lytter and hører? I know they're listening and hearing but "listening to the radio" was accepted and I'm not sure why.
roughly lytter and hører indeed translate to listen and hear. But sometimes the usage in nspecific context is slightly different, as it is the case here.