Those three phrases mean the same thing in almost any circumstance that I can think of. They are all ambiguous too.
All day to one person may be a few hours, to another a full work day, maybe daylight hours to another person, and maybe another person would say it means during all waking hours. I could give you examples all day (which would be a few minutes before I get bored).
So all three of those phrases could mean any of the examples above or something in between. Also when someone says they did something like their homework all day long, that may mean that they had their homework out while they watched t.v., went out for lunch, or talked on the phone. All day is often exaggerated and the only way to truly know what happened is being there or having solid context.