Should I take depreciation for asset, or enter as expense - had rental home for over 27.5 years

Jules

There's a rental home in my name, and it's been rented for over 27.5 years; depreciation on the home has been fully completed. However, we occasionally have an asset, such as a water heater for 2024.

-Should I put that down as an expense, or take depreciation for that?

-If I enter it as an expense, where should I enter it - as a repair, etc.?

-What does the last page of Schedule E mean when I take depreciation for the home or asset? Can you explain the numbers/columns?