Now, that could be a Genealogy.com User Home Page, where is where you are posting this message.
There is a Family Tree Maker User Home Page. You could get there the way you stated in #1.
There is an Ancestry.com User Home Page.
2 - Where did you establish your Account?
Again, FamilyTree Maker, IF you have and use the Family Tree Maker program. Genealogy.com, with or with out the Family Tree Maker program. OR Ancestry.com, again with our with out the Family Tree Maker program.
Question 2: You can post the URL of your User Home page on either of those Surname GenForusm.
To go a step further, you could go to a Location GenForum and do the same.
However, the real question is How do people Search go find you, IF you don't send the URL (Internet Address) Link to folks.
Most search engines will find your User Home Page. Searching on a GenForum or any of The Generations Network 'company' websites should find you. Google will also, probably find you. For example, the Search button at the top of this page will find your user home page.
Question 3: You MAY be able to change your page name by clicking on MyGenealogy.Com button and looking in the Lower Right Corner of that Page for your Account information. What you do NOT want to do is to create another online account.