What is the initiative of the objects animated by the Animate Objects spell?

The Animate Objects spell indicates that the objects act on their turn, but it doesn’t explicitly state what their initiative is. Are they supposed to roll initiative using their Dex modifiers (either individually or with their size class)? This would be as in the Find Familiar spell:

In combat, it rolls its own initiative and acts on its own turn.

Or do they act immediately after the caster? This would be as in the Summon Beast spell:

In combat, the creature shares your initiative count, but it takes its turn immediately after yours.

Or does this simply require a decision by the DM?

When should initiative be rolled during a surprise attack?

This question does a good job explaining how surprise attacks work for the most part, but I’m not sure how such an attack would actually play out, here is what happened in my last game:

There was a group of enemy creatures, and the heroes were successfully avoiding notice nearby (I guess they were effectively hiding), watching the creatures and planning what to do while unnoticed.

After agreeing upon a plan, one of the PCs made a ranged attack against an enemy. This catched the enemy flat-footed against the attack, but the PC became observed by everyone after resolving it.

I decided to roll initiative and start the encounter at this point since it made the most sense at the time, but after reading the rules I’m not sure if this played out correctly.

Should initiative have been rolled just before the attack? This seems unfair to the heroes, since according to Avoid Notice it would force another Stealth check to see if the enemies notice them, but the heroes have not done anything yet to break their hiding. And then, if they succeed on the check, what is the point of the enemy turns?, since the heroes are still unnoticed, the enemies would do nothing until the heroes act.

This leads me to believe that the encounter should have started at the moment the heroes spotted the enemy: initiative is rolled according to Avoid Notice and if the heroes succeed on the Stealth check against the Perception DC of the enemies, they remain unnoticed. And all the watching and planning would have ocurred in Encounter Mode (a very long and pointless encounter for the most part).

If this is the correct approach, the heroes could decide to coordinate and attack all at the same time, by delaying to set their turns one after the other, and readying an attack just before the start of the turn of the first hero, so everyone would use their readied attack and then have their full turn before any enemy gets to act. Is this right?

Can my Primal Companion roll initiative instead of my character?

In Tasha’s Primal Companion feature it doesn’t say that the beast doesn’t roll initiative, just that it acts during the player’s turn. Is that enough to mean that it’s the player that has to roll initiative?

I assume the answer is yes, but it would be nice if you were playing a strength build ranger, or to take advantage of the Primal Bond.

Does Battle Cry happen before or after Initiative is rolled?

The Feat Battle Cry reads

When you roll initiative, you can yell a mighty battle cry and Demoralize an observed foe as a free action. If you’re legendary in Intimidation, you can use a reaction to Demoralize your foe when you critically succeed at an attack roll.

There are similar abilities, such as Hobgoblin Generals’ General’s Cry.

Do effects like this occur before or after initiative is rolled; specifically, does this (potentially) affect the target’s Initiative roll?

if you use Enhance Ability: Cat’s Grace on a creature that rolls initiative, does that creature lose the better roll when the spell ends?

Let’s say the caster uses Enhance Ability and chooses Cat’s Grace on themselves and rolls a 13 and a 16 with advantage on initiative, so they take 16. If the caster then loses Enhance Ability in-combat, or ends concentration on that spell, does their initiative roll revert to 13?

How should one interpret the word “identical” in the initiative rule?

The rule for initiative in PHB read (emphasis mine)

Initiative determines the order of turns during combat. When combat starts, every participant makes a Dexterity check to determine their place in the initiative order. The DM makes one roll for an entire group of identical creatures, so each member of the group acts at the same time.

I usually thought that identical creature stands for creatures of the same type and with the same name: for example, in a situation where a party is fighting 3 trolls and 2 ogres I read the above rule as rolling one d20 for the trolls’ group and one d20 for the ogres’.

Other DMs would extend identical to a wider meaning (see enkryptor’s answer to "Is this house-rule that has each monster/NPC roll initiative separately (even when there are multiple creatures of the same kind) game-breaking?"): for example, a dragon and their kobolds army fighting the party may be considered identical creatures in the sense that they are allies, as belonging to the same group of enemies.

Is there any RAW interpretation of the word identical in this context of initiative roll?

Is this house-rule for initiative game-breaking?

The rules for initiative in PHB read (emphasis mine):

Initiative determines the order of turns during combat. When combat starts, every participant makes a Dexterity check to determine their place in the initiative order. The DM makes one roll for an entire group of identical creatures, so each member of the group acts at the same time.

The DMG offers several alternative options to the above ruling: Initiative Score (i.e. a passive DEX check), Side Initiative (each group rolls a d20, without modifiers), Speed Factor (more uncertainty, less speed). For large groups of enemies, some DMs decide to split them into subgroups (see this answer). I find the ruling about initiative in PHB asymmetric$ ^1$ and none of the listed alternatives really satisfies me.

Would a house rule that allows rolling initiative for each$ ^2$ enemy (even of the same type) be a game-breaking one? Or would there be just minor problems at most?


$ ^1$ I wonder why the PCs can have all different initiative rolls while monsters (even of the same type) should share the same one. They are still different creatures which may react with different speed.

$ ^2$ Do not consider here the issue of rolling a lot of d20s for the initiative (if you consider it a problem).