Giving the steam Game Data to the friend

I had some games installed in my computer and my friend even purchased it but not yet downloaded.
I searched internet about how to transfer game data from 1 pc to another and I understand that but I have a doubt/question in my mind.

If I give a game to my friend from steamapps which he even purchased it then whether there will be a problem from steam bans?

(Just thinking) If there is some data of my game and if I give him that steamapps file then will there any problem to me or him? Any account bans will occur?

Ex, I downloaded Battlefield: Badcompany 2 and there was activation key given by steam to me when I first pressed the play button after downloading. In this case if I give my steamapps\battlefield folder to my friend then will he get the different activation key when he press the play button?

I would say this is pretty safe to copy-paste steamapps/common content between machines (however better look there https://gaming.stackexchange.com/a/214125/171544).

Also, you can think about it as different accounts on the same machine (steamapps/common). They both use the very same files\directories, and no one ever suffered from this.

UPD: sorry havent seen clearly last part of question.

In this case if I give my steamapps\battlefield folder to my friend then will he get the different activation key when he press the play button?

The idea of Steam is Digital rights management (DRM), so it is his responsibility to give each of you proper key.