To what extent would a wizard be able to combine feats to learn to mimic unknown spells?

Question

Searching for how to give a rogue I'm building a sort of eidetic memory, I came across many posts throughout the net about using the feat Keen Mind as a way for wizards to negate having to worry about it in battle. Not having understood Keen Mind's definition in this way, it got me to look at feats in a new way to see how they might be used.

Keen Mind:

[...] You can accurately recall anything you have seen or heard within the past month.

Observant:

[...] If you can see a creature’s mouth while it is speaking a language you understand, you can interpret what it’s saying by reading its lips.

Actor:

[...] You can mimic the speech of another person or the sounds made by other creatures. You must have heard the person speaking, or heard the creature make the sound, for at least 1 minute. A successful Wisdom (Insight) check contested by your Charisma (Deception) check allows a listener to determine that the effect is faked.

Given that spells are broken down to three aspects, Verbal, Somatic, and Material, where the verbal aspect is more about the sound than what's said, could the three feats listed above combine to grant a wizard the ability to replicate any spell he witnesses?

I realize that spells are more complex, so the wizard would have to have the spell slots available, an arcane focus to take care of the material part (limited by the conditions of an arcane focus) and would have to have some insight on how that spellcaster might sound beforehand (granted this can be done by asking around the Magic Guild to show off their favorite spells, and applying what you learned to similar races/classes), but in general, am I correctly understanding how a wizard could use these feats to, in a way, use the enemy's skills against them?

Answer 1

A spell's verbal, somatic, and material components are necessary but not sufficient

The rules have this to say on spell components (emphasis added):

A spell's components are the physical requirements you must meet in order to cast it. Each spell's description indicates whether it requires verbal (V), somatic (S), or material (M) components. If you can't provide one or more of a spell's components, you are unable to cast the spell.

So we know that providing the components is necessary in order to cast the spell, but these are only the physical requirements. To see what other requirements there are we can go back to the beginning of the chapter, in the section called What is a Spell?:

In casting a spell, a character carefully plucks at the invisible strands of raw magic suffusing the world, pins them in place in a particular pattern, sets them vibrating in a specific way, and then releases them to unleash the desired effect--in most cases, all in the span of seconds.

This chapter doesn't explain how a character accomplishes any of these tasks, because that varies from character to character. A cleric may do this by channeling the divine will of their god, a sorcerer does so by projecting their will into the world, and so on. And of course, the specifics of how it works in your world can be different from this.

Regardless, the point is that replicating only the physical components of a spell, i.e. the parts you can observe, is not sufficient to cast the spell, and learning only the physical components of a spell does not grant you an understanding of how that spell works or how to cast it.

Answer 2

No.

The components you supply at the time of casting are but a fraction of what it takes to produce a spell effect—most of what’s needed occurs during preparation. The actual casting is just the finishing touches necessary to trigger the spell.

(Classes that always know certain spells, without preparation, such as the sorcerer, basically have the spell preparation permanently infused into their bodies, so the spells are always “prepared.”)

So supplying the finishing touches does nothing without the preparation. Those feats could reasonably fake casting the spell, but for most spells the lack of apparent effect will give away the game pretty quickly—you might draw a counterspell that way though.

To see this style of magic in action, see the works of Jack Vance—his novels inspired the original magic-users of D&D.

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What the three feated character in the question sees is this,

In casting a spell, a character carefully plucks at the invisible strands of raw magic suffusing the world, pins them in place in a particular pattern, sets them vibrating in a specific way, and then releases them to unleash the desired effect—in most cases, all in the span of seconds.

^{(Basic Rules, p. 81)}

but they do not see all that goes behind it which is ...

Before a spellcaster can use a spell, he or she must have the spell firmly fixed in mind, or must have access to the spell in a magic item. Members of a few classes have a limited list of spells they know that are always fixed in mind. The same thing is true of many magic-using monsters. Other spellcasters, such as clerics and wizards, undergo a process of preparing spells. This process varies for different classes, as detailed in their descriptions.

^{(Basic Rules, p. 81)}