Product Backlog refinement

1. Can you think of anyone on a Scrum Team who would not share responsibility in ensuring that refinement is effective?

2. How are the Development Team presently estimating their capacity?

3. If product value wasn't cumulative each Sprint, how could it then be maximized?

I would highly encourage you attend an in-person Product Owner training class. You will walk away with a lot more clarity on these topics. You could also review the Product Owner Learning Path under Resources.

Dear Ian,

1) i mean to say who shall take initiative as thete is no time-box and no event for refinement. I agree everybody in Scrum Team shall participate.

2) Capacity based on hours. My understanding less than 10% of estimated hours to be utilized for refinement. 

3) I will appreciate if you elaborated specific sentence as i asked. I just want to know its interpretation.

Dear Mark,

I planned detail in-personal training for onward certification may be till next month. Till then fee basics i wanted to get clarified with respect to scrum guide.

1. Who is responsible to facilitate and decide Product backlog refinement?  

From the same area of the Scrum Guide you are trying to understand.

This is an ongoing process in which the Product Owner and the Development Team collaborate on the details of Product Backlog items.

Based on that the responsibility lies on the Product Owner and the Developement Team.

2. What exactly mean by "10% of capacity" in "Refinement usually consume no more than 10% of the capacity of the Development Team. "?? 10% of member OR 10% of estimated hours/days etc. ???

What exactly does capacity mean anywhere else that it is used in the Scrum Guide?  The word "capacity" appears twice in the Scrum Guide.  Once where you are pointing it out and the other in the section that describes Sprint Planning. There it states

The input to this meeting is the Product Backlog, the latest product Increment, projected capacity of the Development Team during the Sprint, and past performance of the Development Team.

So whatever definition you are using for capacity at Sprint Planning is what you would use in this area as well.

3. I am getting confuse about "The Increment is the sum of all the Product Backlog items completed during a Sprint and the value of the increments of all previous Sprints." Can I get more elaboration? 

An increment is a portion of work that is potentially releasable.  The increment of a single Sprint accumulates all previous Sprints until a time that it is deemed ready to be released. The goal of each Sprint is to produce an additional potentially releasable portion of functionality.  At some point the Product Owner will determine that there is enough functionality present in the increment to be released.  Consider that each Sprint is adding to an existing product.  If the increment of that Sprint did not include the entire functionality of the existing product, how could it be potentially releasable?  The only exception to this would be if the increment of a Sprint was the very first portion of an entirely new product.  In that case, there would be nothing prior to include.