How do you string a 5 string banjo?

Joel Walker Sweeney. He thought that the 4-string banjo didn't have good harmony, so between 1831 and 1840, as a present for his niece, he invented a banjo with a 5th string.

The same as on a 4 string. E F F# G G# A which is where the A string takes over and continues up in semitones. The 5th fret of each string is the same as the next string open, except where the B...

It can, but only fitting 5 strings to a neck designed for 6 will change the stresses on the neck and might cause the action and intonation to go out, possibly even damaging the guitar.

Yes.

a modern banjo has between 3 and 12 strings