How many Openings are worth knowing and using?

No, not really. Opening theory is somewhat important. Memorizing more than 4 openings is confusing and pointless for beginner players. Just know the idea of the opening

I think having an opening for d4 and e4 as black and an opening for white are plenty until you get a little stronger. Obviously feel free to mess around with different approaches and see what you like, but the consistent advice I hear is to not worry about openings too much until you're >2000

I like this point Lee, and it was pretty much exactly the rating that I was anticipating. So then  eventually, you either assume one of two things:

a) You have mastered the other components of chess to such a degree it's worth exploring which openings suit your style of play best,

or 

b) You understand that certain defensive openings counter other offensive openings more efficiently, and that their outcomes have significant strategic advantages in the very beginning moves. 

I tend to think that sensibly, A) has the case for shorter time sensitive games, B) has the case for longer games. 

You should learn what's called an opening repertoire.

That means having a response in mind to each of your opponents' moves.

For example:

- I will always start with e4 as white

- If my opponent plays e5, then I will play an Italian

- If my opponent plays e6, then I will play a French Tarrasch

- If my opponent plays c6, then I will play an advanced CaroKann

- If my opponent plays c5, then I will play an Open Sicilian

- If my opponent plays d5, then I will play the mainline Scandinavian

- If my opponent plays Nf6, then I will play the four pawns attack variation of the Alekhine

And now you do the same thing as black...

You don't need to memorise every single opening in existence, but you do need to know the openings that you intend to play.

It might be good to start learning 1-2 for each color right now but don’t spend to much time on it. Focus more so on tactics. When you get to 1450+ people start to play into mainlines more often and they won’t make opening mistakes so I would say start really studying then. But even then study maybe 2-3 openings for each side.

know the end.

What if this is the method or studying approach that arrives me at 1450+? I am already suspecting the comments above. What sort of Rating increases are granted if I play the best defense to an opening, or recognize the best offensive opening moves versus a poorly understood defense. 

- I will always start with e4 as white

- If my opponent plays e5, then I will play Ke2

- If my opponent plays e6, then I will play Ke2

- If my opponent plays c6, then I will play Ke2

- If my opponent plays c5, then I will play Ke2

- If my opponent plays d5, then I will play Ke2

- If my opponent plays Nf6, then I will play Ke2

And now you do the same thing as black.

Not a lot. So you defend vs the opening and come out even? That might avoid some early losing spots, but it's not where most of your chess is going to be, your games will be determined elsewhere. Punishing a bad defense can be nice, though it doesn't guarantee a win either, as the game can quickly slip through the cracks. Not to mention it requires the opponent to play a bad defense. If it's significant enough there's a good chance it was already noticeable anyways. 

You move your pawn 3 squares forward to e4 turn 1 and teleport your king to the other side of the board by move 2? Very impressive. XD

no one expects it and thats how you win

Okay fine, attribute 3/4 the probability that your particular instance is correct.

Granted. el Fin. Done. 

Doesn't answer the question at which point (or rating) does opening knowledge pay off. 

Whether or not it pays its dividends isn't necessarily up to your opinion or experience alone (though I say, odds are in your favor).

I'm learning the openings with similar structures,  that one can transpose to another.

for example: Caro-Kann and Slav

Nah you misunderstand.

White plays 1. e4. Black plays 1... Anything. Then white plays 2. Ke2.

That practice would infer that one is superior to the other in certain circumstances. Amirite?

To get from 1250 up to 1450+, you should still learn an opening repertoire, except you don't need to go into nearly as much detail.

You can just memorise the first 5 moves of each opening and then improvise from there.

Also, I'm going to sound like a broken record for saying this, but: tactics, tactics, tactics.

This brought a big grin to my face. It was some sort of validation that this was a legitimate question, on the idea of whether or or not "opening repertoire" CAN be a difference in your games/rating, not WILL. 

And Tonya, I've been reading your advice, and appreciating it on other post, but I think you know what I meant. Certain circumstances, covers about the range of 1-5 moves. 1-2 we can know generally, that certain openings counter the opposition. Which those 1-2 openings would be the ones we demonstrate in those "Not so certain circumstances".