24 hours isn’t a magic number. I wait until the yeast is done growing. Sometimes I’ll time the starter, as best I can, to pitch into a batch of wort as the starter peaks. Other times, I’ll chill in the refrig and then decant.
Yes, if I have chilled it. If you decant, leave a little beer on top of the yeast, don’t pour it all off.
I’ve never gone beyond a few days, but I’ve heard of others going longer,
Never thought about adding hops. Never had a reason to.
Yes, I use an external magnet to remove the stir magnet before pitching. But be careful with it - see this old post of mine Magnet stronger than glass
