Haligtree is optional and higher level than Farum. You can do Haligtree anytime where as Farum will move the story forward and lock out certain parts of the game
Phase 2 is easier if you ride around behind him and wack on his foot. He'll roll away instead of attacking, rinse repeat. Just have to juke a little bit away if he can get in a swing before you get back behind him.
After experiencing almost all that Elden Ring has to offer, my new passion is watching the endless compilations of rage/fail videos. Many a controller, keyboard and mouse have died to bring us such entertainment.
It doesn't expire in the sense that its usually loaded up with so much sugar that bacteria doesn't grow, but everything will start to go stale no matter how well its sealed.