What sidequests can be done before getting Excalibur II?
Solution 1:
Everything in the game can be achieved, even with a 12-hour speedrun. Take a look at this Excalibur II perfect guide by Atomos199.
Hope you got some time, there is really much to read. Hope you are crazy too... But once more (because I know you cannot believe it at first) : you CAN (does not mean you should) do a perfect game with Excalibur II.