Megaman Zero 2 - Forms

Can someone tell me exactly how to get them?
Gamefaqs are somewhat vague about it. Sure, they give requirements, but it doesn’t explain everything.
They say that for the X form I need to kill 50 things with my buster…

Does it have to be on the same mission?
Does it have to be on the same life? (I.E deaths doesn’t adds up)
Does it have to be on an “active” mission? (The ones currently playing, not reruns you can make trought the operator)
Do I have to finish the game first?
Do the same monsters counts? (Going back and forth to kill more bots, more points?)
Can I get it on my first mission? (The intro?)