Do nurses have to be CPR certified?
To be hired as an RN—yes. To have a license—no.
Yes, nurses MUST have BLS to start the job. PALS and ACLS may come later.
Absolutely, if plan on actually working as an RN. No place will hire you without it. You don't "need" it for your license, but it IS considered a basic necessity and requirement for any nursing position out there.
No. Nurses do not have to be certified BLS (ie to maintain licensure). To be employed however? I doubt you'd find a clinical job of any kind that doesn't require it.
At minimum, nurses need Basic Life Support, or CPR.
Recommended is ACLS or Advanced Cardiac Life Support.
If you're in a specialty like pediatrics, PALS or Pediatric Advanced Life Support is recommended.
There are lots of specialty certifications, including outpatient and med-surg which may or may not be necessary depending on where you work and your own preference.