I have an important question. the animated shield is (very rare). so it's +3? That is to say, an equipped character would have +2 AC (shield base) and +3 for very rare? Thanks for the help.

No. A "Shield +3" is a specific Very Rare magic item. While the "Animated Shield" is also a shield and also Very Rare, its not a "Shield +3". Its rarity comes not from extra AC, but rather from its unique ability to work hands-free.

yessssssssssssssssssss

Quote from PalladiumTurtle >>

How would this interact with the Cleric's/Paladin's use of a Shield as their Holy Symbol for spell casting?  Would you, then, be able to wield a 2 hand weapon and still cast spells?

 Short answer: no. You need to be holding the shield to use the holy symbol on it. If you want to be able to wield a two-handed weapon and still cast spells, you should see if you can get a ruby of the war mage.

See the Sage Advice Compendium: https://www.dndbeyond.com/sources/sac/sage-advice-compendium#Spellcasting.

What’s the amount of interaction needed to use a spellcasting focus? Does it have to be included in the somatic component?

If a spell has a material component, you need to handle that component when you cast the spell. The same rule applies if you’re using a spellcasting focus as the material component. ...

Late to the party, but relatively new to DnD. Didn't see any other responses regarding this, so adding in.

Per the Holy Symbol Description:
"A holy symbol is a representation of a god or pantheon. A cleric or paladin can use a holy symbol as a spellcasting focus, as described in the Spellcasting section. To use the symbol in this way, the caster must hold it in hand, wear it visibly, or bear it on a shield."
You do not have to be holding it for the holy symbol to use it as your focus.

I tend to disagree with you here... the wording states "The shield leaps into the air and hovers in your space to protect you as if you were wielding it, leaving your hands free." In my opinion, the player would be fully capable of using it as a holy symbol.  I'm not pretending to be an expert here, but the statement "as if you were wielding it", implies to me that all rules/mechanics that require "wielding" would then apply.

This is Isbin's +1 Shield.  Poor boob never realized it was also an Animated Shield!  (They never had a wizard in their party to translate the runes on the inside lip.)

Dumb thought: what would happen if your DM was wanting to help the tank character by giving them a mix of this and a Shield of missile attraction? Would the activated shield draw the range attacks to it, or would it automatically move to block any range attacks? My dm gave me a dancing sword during one session and allowed me a shield of missile attraction near the start so this thought has been bugging me for a while.

You can put the emblem on your armor instead

You shouldn't need proficiency for this, in my humble opinion.