Has anyone ever escape from North Korea?

Yes. Some people escape into China, although the Chinese government generally sends refugees from NK back. Some have escaped to South Korea in boats.

The land border between North Korea and South Korea is heavily guarded, fenced, and mined.
Yes. Some people escape into China, although the Chinese government generally sends refugees from NK back. Some have escaped to South Korea in boats.

The land border between North Korea and South Korea is heavily guarded, fenced, and mined.