A few notes about the Rune AU Redefined
Alec is 20 almost 21 when he proposes. They get married on October 8th, 2014. (same day, but 3 years earlier)
Events of the show still occur when Alec is 23 BUT obviously he and Magnus are married.
His 'wedding' to Lydia never occurs because he is married to Magnus.
Valentine is still the main bad guy. But Aldertree, Raj, Robert and the baddies from the Rune AU are still around being a pain in the butt.
(more may be added)