Approved I-140 with pending I-485

[zenith]

Hi,

I have a couple of questions which I hope our Guro's and helpful members could answer.

1. Is it true that if the primary applicant of I-485 dies, the other petition for her family is still valid? If yes where can I read the part that says so?
2. Could the petioner of I-140 withdraw his petition even if it is approved?
3. If Yes, what is the effect on the I-485 pending application?

Thanks a lot in advance.

zenith