Does the Ring of Royal Grandeur still only drop in Act 1 or did they change it up for 2.3?
Can only get it form bounties from act I. Although it might also be possible that it can drop from bonus bounty bags from other acts, I'm not entirely sure about that.
Drops in Act 1 and Act 5 as Act 5 drops all, but as you know how rare it is in Act 1, its deeply deeply unlikely you will ever see it from Act 5, my mate got his from Act 5 but ive never seen any
Bonus caches drop the same things as the act they came from, technically you can get RoRG in A4 caches as well since they just drop all the other cache legendaries but you're still best to farm it in A1.
Four is the one that drops all the other acts, five has its own drops (Helltrapper, Salvation, Pandemonium loop, Soulsmasher and Death's bargain)