DNA/RNA/Peptide Lab Techniques - Denatured, Reduced, and Native States

Can the relevant nucleic acid/peptide be in native, denatured, and reduced forms when analyzed under these lab techniques (listed below)? Which nucleic acid/peptide form(s) makes the most sense for each technique? Which form(s) absolutely will NOT work for each technique?

Lab Techniques (I might be missing some)
Gel electrophoresis
SDS-Page
Western Blotting
Southern Blotting
Northern Blotting
PCR
RT-PCR
Isoelectric focusing

I hope my questions make sense! Also, feel free to include...

DNA/RNA/Peptide Lab Techniques - Denatured, Reduced, and Native States