Being an amateur historian, I mostly used Wikipedia info-boxes for dates, though there is some subjectivity to adjudging the continuity of state lineages. I took into consideration name, territory, language and identity. For the phenomenon of "personal unions" and "commonwealths" it is assumed that in practice this meant one entity dominating and continuing their legacy, while the other's was made redundant. Dates of "independence" were calculated at point of first recognition by a significant power, excluding war-time events. I considered Kingdom of Judah to be ancestral to the State of Israel.
Great quiz! I initially thought that Armenia and Georgia wouldn't have gained their independence until 1991, but it looks like both of them became independent briefly in 1918 (Georgia's independence lasted until 1921, while Armenia's ended in 1920, before they were absorbed into the Soviet Union). That being said, Georgia is listed here as gaining their independence in 1922, but it should be 1918 instead (by 1922 they were part of the Soviet Union).
Nice idea for a quiz, even though it's tricky to ascertain continuity sometimes. I'm Egyptian but I was surprised at it coming at number 2. I never thought of how long an ethnic Egyptian state ceased to exit. I think the whole Fatimid/Ayyubid/Mamluk period could be considered an independent Egypt, just not ethnically ruled by Egyptians. Did you only count ethnic independence?
@Nyackjohn I did consult Wikipedia when I made the quiz. As far as I can tell, Ireland was never an independent country ruled by one leader or by an agreement of equal leaders. It looks like there was a plurality of smaller kingdoms most of the time, some of which weren't even Gaelic but Viking, and they definitely fought each other.
There were a couple who claimed to be High King, but did not get any recognition, nor demonstrate control of most of Ireland. I'm willing to be shown information to the contrary, but https://en.wikipedia.org/wiki/History_of_Ireland_(795%E2%80%931169)#High_kings_with_opposition_(1022_onwards) doesn't identify any concrete ruler or entity that had clear independence and was large enough to be the considered the ancestor of the Republic of Ireland.
At the risk of appearing a complete plank, I didn't read the description properly and initially typed in "Canary Islands" and Iceland popped up... presumably it's so people can type in the Icelandic for Iceland? A bit of a gift though (which possibly twerps like me need)
If you consider the kingdom of Judah to be ancestral to the modern state of Israel, then the last time it was independent should be 63 BCE with the conquest of the Hasmonean Kingdom by Rome.
There were a couple who claimed to be High King, but did not get any recognition, nor demonstrate control of most of Ireland. I'm willing to be shown information to the contrary, but https://en.wikipedia.org/wiki/History_of_Ireland_(795%E2%80%931169)#High_kings_with_opposition_(1022_onwards) doesn't identify any concrete ruler or entity that had clear independence and was large enough to be the considered the ancestor of the Republic of Ireland.