Is it possible to have a non sandbox game

Ok

Currently, no. However, I believe career mode is planned for the next major update.

no

No, not really. I know it's high up on the list of things to add, but there's still no timeline on that yet. I do know some people have been working on a "mod"(I'm not sure if it's really a mod or just very extensive vizzy programming) though that adds a campaign mode of sorts to the game, but I'm not sure about how soon that'll be out, just that it's close to complete atm

Not yet