free if you take a shuttle
The original Six Flags park, Six Flags Over Texas, opened in 1961.
The Six Flags park in Missouri is called Six Flags St Louis, unsurprisingly because it is located in St Louis, MO. It is one of many Six Flags locations in the USA.
In the summer
about 16 bucks or so
The food is not free.
No
no
Six Flags by a long shot.
Yes, a season pass from any Six Flags park is good for all other Six Flags park. If you have season pass parking, it may not be valid at some of the parks.
If you can not find Six Flags St.Louis by using the city St.Louis, Try Eureka, MO, this is the actual location of Six flags in St. Louis.
There is only one Six Flags Great America, however, there are numerous other Six Flags theme parks in North America. (They just aren't called Great America.) Here are a few of the other parks: Six Flags Great Adventure-New Jersey, Six Flags Magic Mountain-California, and Six Flags St. Louis.
Yes they do get to be free!