For example, knowledge can definitely limit your choices. If you do not know something exists, you cannot pursue it or want it.
But if you did, you would be free to do so.
Freedom is not a human made conecept, it is perceived as human. The basic example being someone locked in a cell, and some one not. Simple, lack of freedom and freedom. So why pose pointless questions of what would the free person do that the imprisoned one can't. Freedom is both physical and mental you are right about that.
But...
Consider the following hypothetical situation: You were born and raised in a biodome that is completely shielded from the outside world. No one in the dome knows of the outside and there are no means to leave the dome. It is a self sustaining biosphere and everyone in the dome has all the food/water and clothing they need. Are you free?
A person on the outside would probably say no. That the person in the dome isnt aware of all of the possibilies of existence. Their life is constrained to only the things that exist within the dome. A person in the dome would argue that they are free. They have the ability to do everything they know exists. Anyone on the outside can see that the dome inhabitants knowledge is limited and their options constrained.
Think of people states 'freed' from dictatorships. History has shown that yes they don't know what to do with the freedom they now have, but in time they appreciate it and come to value it very highly. Your example also crosses into truth, as a principle, they people probably at some point did question, 'What was outside?', but were not told the truth, but a lie. Also, if no one were to tell them anything, neither truth not lie, then, human nature would compell them to investigate what lay outside.
But you must realize limits exist no matter what. It is because of those limits that a person can never truely be free.
Every argument must be rational, this is just pedantic. If you are gonna use ridiculous extremes to justify it then you will never be really appreciative of freedom. Freedom is earnt, through toil, whether it be war, or the construction of a space ship, freedom becomes greater as man advances and he can construct and accomplish more. Usually when one questions why can't I do this?
It leads to scientific or technological break through, the 'what if?' will always make us more and more free.
GS