Suddenly In my test tenant it is showing " out of the box templates from Microsoft and any templates saved to the site" in the Site Pages library. I want to create the same functionality to another Tenant, so i can save the modern pages as templates and use them later , can you please suggest how to get this and am i missing any tenant level setting?
This feature is currently in preview and rolling out to Targeted release tenants.
You can setup your tenant to receive these updates earlier as mentioned in this link.
Would recommend that you do this change on demo or test tenants. Because these features are in preview, there is good chance that it could possibly break some existing features.