Mature red blood cells do not have a nucleous. Most of the organells degenerate to make room for the oxygen cargo.
Only Eukaryotes have a Nucleus. However, Prokaryotes have a Nucleoid, a nucleus-like organelle that does not have a nuclear envelope or a nucleolus.
Yes, Eukaryotic cells have DNA in their nucleus.
Yes.
Eukaryotes have a cell nucleus. Prokaryotes do not have a nucleus. Both are cells.