i am assuming your on XBOX? it not l2 its the little clear/white button to pick up a weapon.. secondly you have to fight raiden to unlock him in Orderrealm i believe

I'm not sure what to say about the stage weapon problem you are having. Standing right next to the weapon and pressing L2 is exactly how you pick them up.
I really don't remember how to get Raiden. I do know that the Krypt FAQ that is stickied to this Message Board is correct and has the info.

Nope I have PlayStation 2
Can you be more accurate about Raiden please? He is my last character.

to be honest , i forgot.. but in Orderrealm, its where he stands with all those other people, near center of town,,

Alright I know where that is.

he is in a jail cell in orderrealm with some other guards u have to fight him and he will give u coins then look behind him and open the chest then he will be unlocked

for the xbox .
you have to press the white botton and hold it until it picks up the weapon
I am not sure wich button it is for ps2 but I am pretty sure you have to hold the button for at least a full second.

^^^False Info.^^^
For Raiden I'm pretty sure you DO NOT need to open any chests. Simply fight Raiden and unlock him at D-3 Orderrealm. To unlock his alt. it is in Edenia (you must also fight Raiden to get this) though I'm not sure where.
If you already know this info, then please by all means disgregard my post..

For Raiden you go to Orderrealm (I think it's E-3) and he will be there with some other guards. Just punch him and you'll fight him. I think he does like double damage or somehting like that. But anyway he's easy. Just beat him and he'll give you the key to unlock him. Oh and this is after you beat konquest naturally.