Mu.

https://en.m.wikipedia.org/wiki/Mu_(negative)

See Non-dualistic meaning section.

Depends on what kind of sandwich it was before, and along which axis you cut it, and where you fall on the sandwich alignment chart.

Yes, you do have one or two sandwiches.

Edit: oh dang, I wanted to make the “or” joke so badly that I missed the option to have zero sandwiches.

Assuming a normal cut, this isn't a question about how you define a sandwich, this is a question about the number of servings, and only you can answer that.