Obtaining rewards for missables

Sorry if this has been asked before.

I'm on chapter 3 and I'm trying to do as much as I can in each chapter (following a guide) but I'm struggling with mission 7-1-6 and trying to get the flower cart part.

Can I progress chapters and still reclaim the rewards in a later chapter, or do I have to do it in the specific chapter? I want to go a bit further and get the materia fusion unlocked.