Unique situation

Hello Deepti. First of all good luck to your efforts, and lot of success.

I have never been in such situation, so my thoughts are purely hypothetical but some advice is better then no advice, and I can only hope it will be useful...

In my opinion the main problem here is a single product backlog for multiple products, which goes against the Scrum rules and general logic.

Please remember

Since you were trusted to be a SM for multiple teams, it means that organization who is sponsoring the whole thing is trusting you. So you can influence them easily? 

The most logical thing to do would be to make sure that every product has own product backlog, which actually is easy to achieve by talking with each PO and explaining them that its most logical thing to do?

If the organization orders the same backlog you can call it Organization backlog, to fit into organization standard, and then ask PO's to start product backlog for each item?

Another solution might be to unite products into one bog PRODUCT, unless they compete against one another, and scale the scrum into Nexus(please simply search this site for scaled scrum and Nexus, there is lot of reading-in fact I am currently preparing for Scaled Scrum test myself)

In that case only one product owner should stay though, and those who will go away might actually try to sabotage that decision....

As I have said, I don't pretend to be a specialist-expert of such situation, but I hope my advice helps. If it does please post here, so we both can learn from the outcome

The situation you described is not described in the Scrum Guide as you mentioned.  And as the Scrum Guide states in the End Note

The Scrum framework, as outlined herein, is immutable. While implementing only parts of Scrum is possible, the result is not Scrum. Scrum exists only in its entirety and functions well as a container for other techniques, methodologies, and practices.

If you want to bring the organization around to the Scrum framework as designed, you will need to find ways to get individual Product Backlogs with a unique Scrum Team assigned.  That can be a daunting effort and will not happen quickly. 

So, I'll give you non-Scrum advice based upon real life experience where I found myself in the same situation.  I had the title of Software Engineering Manager. I was doing the work of the Scrum Master responsibility in addition to other duties within the organization.  I'm not going to use Scrum terms because we weren't doing Scrum. I suggest that you try to do the same thing.  You aren't a Scrum Master.  You are a more of a project coordinator or project manager. 

The biggest challenge was getting the Product Managers to cooperate on ordering of the work that needed to be done.  They both had "#1 priority work that had to be done immediately".  As such, the Software Engineers were constantly being pulled in different directions and they had a difficult time getting anything completed. I had to step in and stop the Product Managers from trying to manage my team of Software Engineers.  I took over the work assignments and told the Product Managers what the team would be working on.  Effectively I took over the ordering of the work effort using input from the Product Managers. I built up the roadmap and directed the Engineers to focus on one effort at a time.  We were able to start completing work although the Product Managers weren't happy that they did not always get the work in the time that they had promised to customers.  I wasn't a very popular person with our "money-making" business units but I was very popular with the Engineering, Support, Compliance, and Security units.

Now, my situation was different than yours because I had a job title that allowed me to push my authority.  But you are going to see the same issue.  How will multiple Product Owners work together to order the work across multiple products when there is only 1 team of Developers to do the work and still allow for incremental delivery of value so that empirical value can be derived. I'm not sure how much influence you will be able to have on changing the process so you may want to investigate project management techniques that could help. 

There is a single product backlog though.

Why? What forces are at work? In what way is this lack of transparency over products and their value helpful?

Thank you all so very much for the guidance. Ian there are multiple contending group and priorities. The customer base is totally different and probably these is no handle on how to uniformly create unique priority. There is dedicated scrum master but multiple POs.