If the private key is secured with a passphrase, how to configure the ssh key manager to support non-interactive, password-less ssh login?

How simple to setup a password-less, non-interactive SSH login for shell scripts or batch file?

How to generate public key and private key with Puttygen? How to update Putty-generated public key to the OpenSSH-based authorized_key file in order password-less ssh login to work?

How could you get an automatic SSH login to remote SSH server, so-called password-less SSH login.

Do you encounter an inactive SSH session keeping disconnected, especially when you SSH to host over a slow network link, VPN or router that disconnect idle connection?