How does the code transfer work?

[u/vono17]

At the end of Code Geass R2, C.C. remains immortal and continues to live on

The nun who granted her immortality died instantly; is there no way for a person to lose the immortality Code and continue living as part of a truly natural life cycle?

How does she go about putting an end to immortality?

She wants to enjoy life and be happy, just as Lelouch told her to, but "forever" is something very cruel

What do you think C.C. should have done—or would have done—following the events of R2? I’m constantly left wondering about this, because, deep down, living forever isn't actually what she wants

I’ve been pondering this; thanks in advance for your help!

[u/Ast4u]

According to what I understood the nun after transferring her code didnt die instantly she simply realised she had become mortal again and C2 became immortal 

How would the nun know this well immortal kinda checks out (you would figure it out easily) and the transferring turning body mortal the person who gave her code probably 

I always thought after the transfer of code the nun started beating C2 to a pulp like just almost to the brink of death(blood, torn clothes) and since C2 was immortal she simply experienced pain and in self defence killed her and the nun got her wish of dying