How to use Yubikey (openpgp) on another computer ?


I’m new to the GnuPG (OpenPGP) World, and I already have a Yubikey. today I spent hours to work and learn about this things. I read documents from Yubico “Using Your YubiKey with OpenPGP” with “CMD” on Windows, and How to use Kleopatra. But there are some problems I still don’t understand, Please help me :
1 - How to know my certificates in Kleopatra are only public key or included private key ? (For now, right click and see that “Backup secret key” is unavailable to use, which mean only public key).
2 - I have imported my OpenPGP key into Yubikey, But I don’t know what to do if i reinstall my PC or want to use my Yubikey on another PC ?
2-1 - For now, As i understanding, When followed Yubico documents, my private key was imported into Yubikey, So i only need imported my Public key (from keyserver or file i have exported or using “Create OpenPGP Key” function from Smartcards menu) and set it “trust” to “max level”, and then I can sign/encrypt/decrypt files ?
2-2 - But the thing made me confused is When using funtions “Create OpenPGP Key” from Smartcards menu (Kleopatra), I can create a new name and/or email address and that public key still valid ? What !!!
3 - How to know my private key have imported into my Yubikey ? on Kleopatra Smartcards menu : I saw Signature, Encryption, Authentication are already configured, that mean my Private key imported into Yubikey ?
4 - I saw that in Smartcard management has pubkey URL, I tried to upload my public key to my hosting and then trying to “fetch” to let see how it goes… The result is : I need to use “CMD” as “Admin” to able to fetch … is it right? and it is necessary (I thought if i use my hosting, it maybe has more “trust” ? I am thinking about Revocation certificate, But still don’t know how to use it ?

Sorry for my bad english. Thank you in advance.

Hello @longcoi

When you own a private key the key is formatted with a bold font in Kleopatra.

Yes, but you should store the public key somewhere where you can be sure that no other one can modify it (I would not trust an external server enough) because in that case the keys would not fit together and you would not be able to do encryption with Gpg.

The “Create OpenPGP Key” Button will be gone in the next release: ⚓ T7113 Kleopatra: Remove "Create OpenPGP key" from OpenPGP smart card tab
The feature was intended to create an OpenPGP Certificate from a S/MIME Key, but this is something very few people need. For all others: Do not use this action (if you did not permanently loose your original public key)!

Compare the fingerprints. If you see something in the smart card tab then some keys are on the Yubikey but those might not be the ones you want.
If you have the Public Key for the keys on the smart card available in your keyring/keybox on your computer, you can click on “Show Details” behind a fingerprint. If this is greyed out the public key is not available.