Yes the lower hole is square and the upper hole is round. There is no sign of any floor fixing holesthe lack of floor fixing may preclude it being a tram seat. a tram seat would typically not have an arm rest either. neither of these should be a reason to conclude that it isn't though.
the lower hole appears to be square which suggest something ended there with a square to stop it rotating.
Yes both ends are the same. I wondered about them being joined to others but it would have been a peculiar connecting system. The parasol idea would workYes, that was my thinking. Are both ends the same? It could just be something like a support for an awning or parasol as pcb1962 suggests? Intriguing?