Odin Sidequest
You have 20 minutes to do this quest I'll guide you through it so here we go. The first part is easy, just follow the various staircases until you reach an altar which is actually an elevator. When you get off the elevator you'll find two ladders. The one on the right leads to an aero draw point,while the left one leads to a room full of machinery. Climb the left ladder, flip the swith inside the room,then go back down the ladder. You'll notice that the altar in front of the elevator is now lit. Upon examining it a staircase will appear on the right. Follow the stairs to the top. Their's a large demon statue with one red eye on the next level. Climb the short ladder on the left, take the eye from the statue,and then climb up the stairs on the right side of the area to the top of the tower. Go to the left and climb the side of the dome to find a second demon statue with one red eye. Place the left eye in the statue and a code will appear. REMEMBER THE CODE. Take both eyes out of the statue and go back down to the first statue, place both eyes into the statue then you'll see a place to input the code. After entering the code useing the directional button, a door below will open and inside is Odin. Odin will not attack you so hurry up he has about 1300~31,000 HP depending on your level. For beating him you'll get Odin's card, 20 AP, and Odin will now assist you from time to time in battles.

Tonberry Sidequest
Before you start this quest I suggest that you have a lot of pheonix downs and hi potions. Ok towards the begining of the tower its like the circle part, you must defeat 18~22 tonberrys to lure out the tonberry king the little tonberrys may not look like much but they have one hit kills.....and around 20,000 HP. If a tonberry gets close enough it'll start useing its knife which can cause close to 4,000 points of damage...after defeating enough tonberry the tonberry king will come out right after the last tonberry you just beat he has around 2500~250,000 depending on your level. This battle may take up to a half an hour.

Cactuar Island Sidequest
Cactuar Island is a small island on the southeast corner of the esthar continent. On the island you will see a small green figure kinda jumping all over the island it is known as the Jumbo Cactuar. If you defeat it you'll get the cactuar GF. Heres a guide for beating the GF.
Jumbo Cactuar: HP 6,000~60,000 AP 20 weak vs water
This battle is all about patience and controlled attacks. The Jumbo Cactuar utillizes a nasty, random counterattack called 10,000 needles. This attack causes more then 10,000 points of damage, which can't be reduced by spells like protect. The rest of the jumbo cactuars attacks are strong but nothing to worry about. Have one of your characters serve as a "medic" for the entire fight. Your "medic" will be very busy reviving the other two characters each time they're hit by the 10,000 needles counterattack. As long as the "medic" never attacks and you constantly use recover or cure spells to keep their HP at maximum, you'll never have trouble reviving downed party members. Of the remaining two attacking characters, focus one on constantly using water magic or physical attacks. The other should concentrate on repeatedly summoning Leviathan, it can cause around 9999 points of damage. After causing substantial damage to the Jumbo Cactuar, you may see a message stating that the jumbo cactuar is hesitating. BE VERY CAREFUL AT THIS POINT!! This means its thinking about running away. You must QUICKLY finish off the boss. GOOD LUCK