The leasing office cannot unilaterally revise a lease after it has been signed. Only amendments signed by both parties are binding, just like...

Unless your lease has some obscure co-tenant eviction provision, only the LL can evict or remove your co-tenant from the lease.

This is likely an accountant question.

You can probably use either one. Addresses change over time, and this is likely for notices, like where to send the confirmation letter after your...

What does your lease say about replacement keys?

A.R.S. § 33-1375(B). The landlord or the tenant may terminate a month-to-month tenancy by a written notice given to the other at least thirty days...

There should be time periods specified within the contract itself depending on which diligence/inspection period you are currently in.

Review the Arizona Residential Landlord-Tenant Act, Chapter 10 of Title 33 of the Arizona Revised...

Sure...just be prepared that you may have to make both payments...

This is not the LL's issue, as they aren't responsible for 3rd party actors. Call the police...you have an unauthorized occupant.