Wildcard challenge

Finding files with spaces from a command prompt might not be immediately obvious. Using quotes is the answer.

1. List all files with a space: dir "* *"
2. List all files that start with a space: dir " *"
3. List all files that end with a space: ???

#3 is a bit more challenging. Normalization has something to do with the answer.

The real challenge is how do you find files with periods??

1. List all files with a period: ???
2. List all files that start with a period: ???
3. List all files that end with a period: ???

Can they all even be done? If not, why? If you have an answer, why does it work?