Has it happened before? A so-called black start, starting up an entire grid from complete power-down, is a complicated thing to do. Might take days or weeks to get everyone online if unlucky. Where I live, with about the same population size as Cuba according to Wikipedia, there are protocols for doing it in a way that should work, but it has never been done in practice, which is of course both good and bad...
Discussion
I don’t know but I’ve never heard about this happening before.
Can’t imagine energizing an entire grid.
You start with the power plants that require the least power for their own operation, use diesel generators to power them (controls, excitation windings, systems for fuel or whatever power source they use, etc.), start them up and bring them online to the grid, with all branches and load disconnected, except the power plants that require a bit more to power up, then rinse and repeat, probably also connecting load as required, for minimum load and probably also to keep the power factor within reasonable limits (not sure how important the latter is with such low load, but I guess it could be).
If done out of sequence, can a grid be irreparably damaged?
Usually there are protection circuits that kick in, but it's probably not impossible to do some damage, at least to individual power plants or transformer/switching stations. Starting the power plants in the wrong sequence is impossible, since there's not enough power to do so, and if it was possible, it probably wouldn't be the wrong sequence.