When you get to Agrabah, keep walking through those sorta keyhole looking arches until you see a raggy old street guy. Talk to him, then make your way back the way you came. Street guy will ask you to look for his friend. Continue through the arch until you are prompted with a cutscene. Follow the sound, and prepare for your next boss battle.
Jafar is a pretty easy battle. This strategy is rather repetitive, but it's worth it. As soon as the battle starts, nail Jafar with every command you've got. He will soon teleport away. Find the wall he's on, and run right up to it, but don't jump up. Jafar will fire a spell at you, but it won't hit you if you're right up against the wall. Use the Metal Blox to reach him, then attack again. Jafar will teleport to another wall. Once again, run up to the wall, wait for his spell, then attack. See what I mean about repetitive? Continue to do the same until the battle ends.
After the battle you'll have to find that street guy. His name's Aladdin. He's no longer at the Palace Gates, but at the Plaza where you first arrived. Talk to him, and you'll finally find out why I called this section the wrath of Jafar. He's obviously a little angry about being beaten by a little kid, so he wishes for new powers. That power, is the ability to freeze time. So he manages to freeze the whole of Agrabah. Except you, because you're special. Now onto to buisness. You're going to have to chase that little red bird around. His name is Iago. Unfortunately, I can't really help you with this one, because Iago is really random, and has no specific flight pattern. Watch out for Phantoim Jafar though. He will steal you're time. Successfully catch Iago 3 times to get the lamp back. After you catch him, Genie will take you to the Cave of Wonders, who isn't really being to wonderful to you right now. You'll have to enter the system sector located to the left of the cave to get him to open his mouth. Should you come out of the sector alive, enter the cave. Follow the path until you reach a waetrfall of sand (?). Retrace your steps past the boulders. Head down the left path, and you should find a sector on the wall somewhere. In this sector you will discover a new type of blox called Magnet Blox. These extremely annoying blox will pull you towards them, which is a bit of a bummer. Once you're out of the sector, head back to the waterfall of sand (?) and Hey Presto! It's gone! Enter the newly revealed area, and make your way to the big platform of Metal Blox. It will slowly descend while you get to fight off hoards of Heartless. How fun! When you it finally stops, prepare for the next epic battle.
Jafar is an ignorant little prick, so he's gone and hidden the keyhole. So it's your job to find it. It is extremely easy, just go and smash every Bug Blox in sight until you find. Then you'll have to fight Jafar again, but this time he's more powerful than ever...
Genie Jafar can be very challenging. The genie himself is not the one you'll be attacking, but his pitiful lackey Iago. However, Iago won't be the one attacking you, but the genie himself. Confused? Use Dodge Roll to avoid Jafar's boulders, and block his delay beams back at him. This gives you two advantages. 1) It slows down Iago so you can smash him to a pulp and 2) It keeps Jafar out of action for a while.
After you think you've beat him, he just comes back, but this time with a whole lot of annoying blox. It's more of a wild goose chase than anything. Use the same startegy before, and catch that little rascal Iago!
After beating Jafar, you'll be savagely attacked in a cutscene...