[kiripanda]

1.
^9999[0-9][0-9]\.n[0-9][0-9]$
^9999[0-9][0-9][0-9][0-9]\.n[0-9][0-9]$
2.
прочитайте findstr/?
3.
просто dir /b/a-d kgt*.txt shk*.txt ukp*.txt