The code for the rocket is circle square x x

The place you can find the Cursed Ring is in Mideel examine the lock door then go to that old guy sitting at the house on the right, go behind him, and you'll hear a crack, press Circle and go back to the door break it then answer the guy's question true fully. And the Cursed Ring is yours!!!!

Getting Yuffie: Go to the forest near Junon and pick a few fights in DISC ONE  the you'll fight Yuffie win, and then you'll go to a field with a save point. DON'T TOUCH IT then talk to her and don't affend her in anyways and yes asking her for her name is affending her. Leave and you'll get to name her then she is yours to control.

Yuffie's subquest: Go to Wutai in the island to the west then use the Tiny Bronco go to Wutai and you'll lose your materia find Yuffie fight Rapps (warning you'll have to fight him WITHOUT your materia.) after that you'll get your materia back.

Getting Vincent: Open the safe in Nibelhim and then go into the basement open the door talk to the center coffin A LOT of times leave and he'll join you.

W-Item trick: Get the W-Item Materia then use a item you want more of then press circle again put not twice only once then canel you'll get one more of that item do it over and over again to the amount desire.