Question about vertex normal elements

Hello, everyone

I am pretty new to Vulkan, so I have three simple questions

  1. Are there cases such that obj or bin (in gltf) files don’t have normal vectors ?

  2. If yes, is it possible for me to create light (diffuse, ambient etc) or do ray tracing etc on materials inside (without normal) ?

  3. What are standard or well-known free tools which edit obj files or gltf (bin) files ?

Thank you and have a nice day