What are the release dates for Sneak Previews - 1975 Take 2 Movie Monsters 4-21?

Please provide more context. It seems you're asking for the release dates of a specific episode of the show "Sneak Previews" but the provided information is unclear.

To help me understand your request, could you clarify the following:

* "Sneak Previews - 1975 Take 2 Movie Monsters 4-21": Is this a specific episode title? If so, can you confirm the full episode title?

* "4-21": What does this refer to? A date? A season/episode number?

With more information, I can help you find the release date for this episode of "Sneak Previews."