Advice needed - Sand / Chemical cleaning / Staining required?

Hi all!

We moved into our new place recently and want to stay on top of deck maintenance. Never own a deck until recently so just want to pick some of your brains here on what to do next?

The deck does not look too old but I don't think it's very new either (we don't know when it was the last re-polished by the previous owner). There is a small section of the deck that is most weathered because it is exposed.

Looking at the pictures, do I need to re-sand or use deck cleaner chemical (eg. Restore-A-Deck) before re-staining it? Or just the weathered section?

Do I even need to do that - some people are telling me that a simple soap + pressure washer is enough... Thanks for sharing and helping out guys.