1) I've NEVER seen a game that didn't let you resubscribe and reactivate the same account. There have been dozens of MMO's that I've played over the years and I have yet to see a single one penalize you for canceling. I would be astounded if SE did this.

2) From all I've seen and read, any new time would not be added until the initial subscription ran out. So in your example of a 90 day subscription, you'd need to wait 90 days before you would be charged again.

Now all of that aside, I think you may not be understanding how and where Fantasia is coming from. So far as I know, these are a reward for loyalty/veteran status on the account. As I understand it, once the account qualifies for the milestone, it's qualified. There is no way to go back and hit 30 days a second time. Those milestones are for the lifetime of the account.