1. We are not aware of any problems with running WinSCP on Windows Server 2025: https://winscp.net/eng/docs/requirements#client
   
2. The "relay server" is rather vague term. If you mean if WinSCP can connect through SSH tunnel, then yes. Though it does not go along with your next question. So I'm not sure what you mean. Can you be more specific?
   
3. "AWS Transfer Family" is SFTP/FTP interface to Amazon S3. WinSCP can use both SFTP and FTP. But it also supports S3 natively.
   

Please confirm the following about WinSCP 6.5.4:

1. Does it run smoothly on Windows 2025?
   
2. Can it upload and download data via a relay server?
   
3. Can it connect to AWS Transfer Family without issues?
   

Thank you in advance for your assistance.