Black 2 Key Link mechanics?

Question

Can a completed Black 2 and White 2 send keys to a newly created save file of Black 2?

Because I got a completed Black 2 and White 2 (bought both games with pre-existing save files) and a new Black 2 (2nd B2 cartridge) and I wanna play the new game with a challenge but I don't know if it will mess up my new save file if I send keys that are also obtainable in the game eventually.

(i.e. getting Challenge Key right from the start of Black 2 even if I can get it post game in Black 2, getting the Iron Chamber Key before catching Regirock in Black 2)

Are there any requirements for the cartridge receiving the key?

Because I'm only at the part where I'm about to receive a starter right now.

Do activating certain keys like the Tower Key affect the story before I get to that area?

Correlated to the question above, if I activate the Tower Key immediately before reaching that area of the game, will that affect things?

(i.e. changing Black City to White Forest immediately from the start in Black 2, activating the Challenge Key, activating the Regice Key before beating Regirock)

This is my first time learning about these keys! Cheers!

Comments

This probably doesn't answer the question, but https://bulbapedia.bulbagarden.net/wiki/Key_System

Answer 1

These keys can be sent to other Black 2 and White 2 games to unlock features in that particular game, or you can use them in your own game. NOTE: It seems you cannot transfer a key from one cartridge, restart that game, and send the same key back. Many people have tried this with the Challenge Mode Key and have failed.

You cannot start a new game on Challenge Mode. The only way to start a new game on Challenge Mode is to erase your original save data after beating the game, and then have someone else transfer that key over to your game. Super fun.

The only way to start a new game on challenge mode is to erase all your data, then have someone transfer over challenge mode to your game using their game.

And for the towers and the Underground Ruins, it does not affect anything other than changing the location to what you set the key as, (if that makes sense.) As neither of these places correlate with the story, and are both post game, nothing should change or be affected.

Source
Source

Comments

I don't think this is what OP is trying to do. They want to send challenge mode from a completed B2 cartridge to a new and separate B2 cartridge -- the source in the answer actually suggests this is possible.
The answer also doesn't address the second and third questions.

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Edited!