Can we submit another possible opening from the same work we'd submitted before?
I believe that all chapters need a opening worthy of starting the book. Why should the reader settle for a bland chapter? Can we submit openings to chapters other than chapter 1?
If the feedback you received from your opening submission has led you to go a totally different way, you may submit your new opening. If you've merely edited it, and it's recognizable as the same opening, no.
As for chapters, I feel certain some people would submit the opening to every chapter in their book if this were allowed. Plus, I prefer not to preface the New Beginnings with explanations of what's happening. In the book, the reader may be familiar with the setting and character and backstory at the opening of a new chapter.
On the other hand, we tend to run low at times, so for starters, a compromise:
It's not unusual for an early chapter of a novel (unless it's written in first person) to introduce a new POV, a new main character whose story will eventually intersect with that of a previously introduced character. For instance, in The Da Vinci Code, chapter one stars Robert Langdon. Chapter two stars Silas. Chapter two could have been chapter one (eliminating the first three words). If this describes your book and you want to submit the opening to the later chapter, feel free.