Spell Animate Dead

4 skeletons or zombies my control.   Playing 5.14 edition, race Elf.  Questions:

What time do you usually cast the spell to keep them under your control?

Do you usually cast it before or after your rest?

Must we wait close to 24 hours before casting the spell to keep them under your control?

If I have like 3 Undead under my control and I cast the spell again at 24 hours for continue control, could it also Animate pile of bones or corpse for the 4th Undead at the same time?

When casting the spell to keep them under your control, do the 4 Undead all need to be within 10 feet of myself?

If my Undead falls into water, can they do things like swim, walk out of the water etc?

Side note, does Spell Feather Fall effect Undead or character while in water?  If so, in what way?

I agree with the answers wagnarokkr gave. Just to add to me #3 is also a no because of the way I read this sentence in blue:

The creature is under your control for 24 hours, after which it stops obeying any command you’ve given it. To maintain control of the creature for another 24 hours, you must cast this spell on the creature again before the current 24-hour period ends. This use of the spell reasserts your control over up to four creatures you have animated with this spell rather than animating a new creature.