Here is another help doc About hosted web layers—ArcGIS Online Help | ArcGIS
Any of those will bring you to many resources.
Your user name should work, assuming it is at least shared with you or a group you are in. But it's all layers of the hosted layers, maps, groups, etc. If any of them are totally private it make be an issues. Multiple layers.
re: the ArcGIS Server...you would know since it wold be something in your work environment. But if you only have a free developer ArcGIS online, there may be other limitations too.