as I said in title, is it possible to search based on custom field value and exclude all others?
Example:
I have custom field named “gender” and custom post type “people”. It is easy to make search just in “people”, but is it possible to filtre “people” by “gender” in result list?
Sure, that should be doable. You can choose the desired post type to search for under the General Options ->Sources panel. Then you can create a custom field based filter for it.