Describe who you might submit to and how.
I submit to the woman I love. I submit in body, mind, and spirit. It is how I display the strength of my love for her.
No clue if I answered "how" in that. I don't even understand how to answer that.
Are you exclusively submissive in marriage or just in the bedroom?
Well, seeing as I have never been married... none of the above. I was engaged to my first Mistress. During the latter portion of my time with T things did turn into bedroom only.
To answer the question I believe they are asking... I submit in life to the one I love. It extends beyond the bedroom and dominates my thoughts.
Are you submissive only in the context of a scene or in a role or throughout your daily life?
Both role and daily life. I have to put on my alpha face at work and around strangers. In private life I am fine as a submissive in all aspects, but how submissive I am varies by my role at the time. e.g. I will be different if I am doing chores, worshipping her body, being disciplined, nursing her back to health when she is sick, etc.
I try to adapt as needed and act with enough "freedom" as necessary to accomplish my desired tasks.
Are you submissive to play partners or only in the context of a relationship?
I have done the play partner thing back when I was newer and between relationships. It is not something I desire but I won't say I wouldn't consider it again if I found myself single.
As things are I only submit to the one I love or anyone she directs me to serve, but I see that as being submissive to her and not "submitting to someone else."