Is pyramid a proper noun

Answer 1

No, the noun pyramid is a common noun, a word for any pyramid of any kind.

A proper noun is the name of a specific person, place, thing, or a title; for example:

• Walter Pyramid (sports venue), Long Beach, CA; named for Dr. Mike and Arline Walter.
• Pyramid Valley, Canterbury, New Zealand
• Pyramid of the Moon, Teotihuacan, Mexico
• Pyramid Street, Ansonia, CT or Pyramid Street, San Diego, CA
• Pyramid Brand Razor, Geneva Cutlery Co.
• "Pyramids", a novel by Terry Pratchett