It appears you can, and that they do ship to Greece. But to be sure, go to the shop and buy it, before you pay you will be able to follow the checkout procedure and verify all that.
As far as Cubase LE 5 without an e-license, I don’t know, but since they offer that particular upgrade they must have a method in place to accommodate this. Do you have a system it can be installed on?
edit 2: see https://www.steinberg.net/forums/viewtopic.php?t=120657
edit 1- ownership doesn’t need to be proved before buying, the the ELC will look for a license that matches the upgrade product purchased.