When you go into the final land (the world that never was) play through it and you will eventually meet up with him and he will become your partner.
No. Riku never dies in Kingdom Hearts II.
No you can't. But if you have the Kingdom Hearts 358/2 Days for DS you can play as Riku in mission mode.
Yes, they do find Riku at The World That Never Was.
I don't think you can
Roxas sora and riku of course
You kill xemnas with the help of riku
Oh yeah, he's adorable. Even going up to kingdom hearts 2
At the end of the game in the Land of Darkness, you'll soon meet Riku when he brings Kairi back to you. He'll soon join you to fight and destroy Xemnas. Unfortunately, you can't play as Riku in Kingdom Hearts 2.
In Kingdom Hearts 2 Riku gives Kairi a keyblade and she uses it to help Sora with Riku fighting Heartless in The World That Never Was.
Riku is only playable towards the end of Kingdom Hearts II, for a short period of time. During the final boss battle against Xemnas, Sora is captured and Riku must stop Xemnas from destroying him. It's only a brief sequence and is nothing permanent.
If you really concentrate on it, you can make it happen.
You can't give Riku a keyblade, he just gets it in Kingdom Hearts 1 when he goes in the Door To Darkness. AA: Riku is just a world specific ally so you cant change his weapon