Just look at the Constitutions of pre-civil war Southern states. https://library.si.edu/digital-library/book/suppressedbooka0...
IMO, what defines a democracy is large segments of the population having a meaningful vote rather than requiring some ideal implementation.
How did you come to that conclusion? It seems like ahistorical nonsense to me.
https://www.jstor.org/stable/20752195?seq=1#page_scan_tab_co...
By comparison England lasted from 886 to 1642 without open civil war. At the extreme Harappan civilization seems to have lasted 2,000 years without an open civil war or really any major wars.
But yes, if you exclude all the civil wars then England had no civil wars during that time period.
Hundred Year War is hardly a civil war existing as it did between multiple countries.
Smaller conflicts like Buckingham's rebellion are excluded much the same ways as I ignored most of these: https://en.m.wikipedia.org/wiki/List_of_rebellions_in_the_Un.... Along with a host of unmentioned smaller slave revolts.
The War of the Roses was is arguable if it’s a civil war. I and many others disagree (see above Wikipedia link).
Democracies have other benefits, but stability does not seem to be one of them.
PS: I am ignoring assassinations and power struggles as we have lost 4 sitting US presidents without it being considered a civil war.