I just recently found the game it took me a while to figure out that the different challenges go from bottom to top instead of the more usual top to bottom. Also: Should the gateway mission be available before somebody finished the previous levels?

You must have dig the entry of your nest to access to the formicarium challenge but make first the levels, you can watch the Rayalot's plays on youtube to know what to do in insane
In the game of ants, you play or you die.

Thanks for the plug! 

You can also watch Balanite's videos for no commentary.  Either of us (although he's been offline for a while) can also answer questions you have about beating any of the levels in any difficulty (although my 1.2 tends to be rusty). 
And on the sixth day, God created ant in his own image, and gave them dominion over the earth and all of its creatures.  Amen.