Terraria – Can you pause Terraria

As of Terraria 1.6, there are four dedicated Ammo slots in your inventory. Applicable ammunition in these slots is consumed first, from the top slot to the bottom slot.

After that, and in previous versions of Terraria without the Ammo slots, it uses the first type in your inventory starting at the top-left and working right. So the highest arrow is used, and when tied for height, the furthest left is used.

This also applies to other ammunition.

All of the comments you've received pretty much collectively give you the answer.

All of those enemies do spawn in 1.1.2; they're very rare, though, and require the right conditions/ biome to spawn. Water candles and battle potions will increase their spawn rate, but at the end of the day a lot of it is luck.

The groom spawns on the surface during blood moons, and Tim spawns at random underground (stone layer). Doctor Bones spawns in the surface or underground jungle at night, and more commonly during a blood moon.

So all you can really do is wander around, take advantage of the blood moons and of battle potions/ water candles, and hope for the best! You'll encounter them eventually if you keep at it.