As an undergraduate student, should I put my temporary address and manuscript on my CV? I'm an undergrad applying to REUs. I've done an REU before and taken independent research classes, but I'm afraid that will only look bad since I don't have any publications in spite of my research experience. I have a manuscript we're planning to submit. I know you're generally not supposed to indicate manuscripts on your CV if they haven't even been submitted, but does that look as iffy for undergrads as it does for a grad student/beyond?

Most of the CV templates I've seen online for students include their addresses. Is that just for the purposes of receiving physical mail? I don't really have an address when school isn't in session, but one of my research advisors lets me use her address for mail. Would that be fine or do they need to know where I live for some reason?
For an undergrad, it is fine to list papers that are not yet submitted.  List them as "in preparation".  Also, if the REU requires letters of recommendation, ask your letter writers to comment on the status and quality of the project.

Yes, the address is just in case someone needs to send you physical mail.  Any place where mail will reach you is fine.  These days I'd say you could just leave it off, since it's unlikely anyone would actually need to do that.  If the program is limited based on place of residency, there would be a specific question on the application for that.