What's different between forrige and siste?
Forrige is previous and siste is last.
'Forrige uke kveld' med John Oliver!
Why is the last week not accepted?
Because "last week" is not the same meaning as "the last week".
I put "Forreige" and it wasn't marked as a typographical error. Is this an error or an alternative, possibly archaic spelling of "forrige"?