How can you limit the levels of the open seats? For example, I only want to invite people with levels between 10 to 30 for the open seats in a game I created. Can that be done? Thanks.

Yes.

In open seats under settings, you have an option to give Minimum as well as Maximum Player's level. It is the first option too.

Sorry, but I don't see that. In the Open Seat Prerequisites I only see a Minimum option. I don't see a Maximum option. Am I still missing it? Thanks!

You have to use the old UI for game creation to get the option. UJS only has the 3 option.
Flash, has many more prereq options https://www.warzone.com/ChangeWebMode

Ok, but what happens if I create the game in Flash but then go back to UJS afterwards?

The pro strat is to make a template in Flash with the prereq you want and save that template. Then, unless you enter the prereq section in UJS you can use that template with those prereq in UJS and change anything else.

Or you could just make the game in flash.

If it's a one time thing you are doing, just go for the flash way. Otherwise, making a template is the best option.

So basically what you are saying is that if I create the template in Flash with a level min and max, and then if I use the same template in UJS later then the min and max are still there (but kind of hidden). Is that right?

Thanks!