The players won’t know they need to go to the Amber Temple right away, so I think it’s fine to leave them there.
The Arcanaloth is not in Strahd’s tomb. It’s checking the out the mystical dark powers stuff.
In the case of Yugoloths, back during the lead up to 5e they just asked during the playtest what the customers would like them to be called Daemon or Yugoloth. Yugoloth won the poll.
Baldman Games has posted the first update to the Legends of Greyhawk storyline based on the outcome of the Battle of Emridy Meadows which was played back at Magiccon.
https://www.baldmangames.com/2025/03/12/the-battle-of-emridy-meadows/
Reference cards are already sold they are not new. The Essentials kit several years back also came with a bunch of reference cards a lot like the ones shown in this starter set.
That sounds like it’s mostly random and it says later they just start changing with time until they become a unique being like a demon lord.
For devils it explicitly doesn’t matter.
According to that one thing that I don't really understand. The most recent lore is that Devils can't have kids at all expect with mortals. And I prefer it that way myself. Fiends don't have to have anything like normal biology that makes sense.
Erinyes are noted as the sole exception in Faces of Evil.
But Erinyes are presented very differently in 1e and 2e as they are more Devil versions of Succubi rather than their more modern Fury incarnation.
2e Faces of evil says Demons can’t breed with each other cause female demons are infertile.
Edit: Sorry mixed it up, demons can breed according to that book, devils can’t.