how do I save only 1 year of photos on my device and the rest on my Icloud

You can't. But see the 'Save space on your device' section in:

Set up and use iCloud Photos - Apple Support

Flipfonow wrote:

I have so much photos that is saved on my phone. Is there a way to have only the recent 1 year photos on my phone and everything else is in Icloud?

Not an option when using the iCloud Photo Library.

It's the entire library or nothing.