Current state of chunk unloading and distance limits?

1. On a dedicated server with everyone offline, does the game entirely pause? e.g. no plants growing or drills drilling

2. Is it still true that stationary drills drill at half speed when very far away? In this case, let's say "very far away" means the drills are in The Shimmering Frontier and The Passage, and you're at The Core.

3. When you go far away from an area do mobs start to despawn, or when you restart the server do mobs despawn? Do they ever despawn? I know they only spawn around a player but I'm not sure what happens as you move and as you warp around to different waypoints then.

A lot of search results on this stuff take me to 4 year old posts, so just wondering what the current state of things is on the current latest version of the game, 1.2.1.5 at the time of this writing.