predefine custom keys & custom selection

I need 2 things
1. i need to disallow adding new custom field by typing the new key – i want to show there only few predefined custom keys i want

2. I need a “select” customfield 2 – explanation: i need to define e.g. “the county” for the post. We have 18 counties, so I want to to allow editor to select one of that 18 counties i predefine. It should be also multiselect – so e.g. more counties per one post.

is there any such option/plugin?