Ubuntu 7.04

If i Build my game on Linux can i after open the game on Ubuntu 7.04 .

From Unity official website:

“While in preview mode, we will only be offering official support for Ubuntu 10.04 or later, with a graphics card that has vendor-made drivers installed.”

So no, it might not work for Ubuntu versions older than Ubuntu 10.04 and you are unlikely to receive official support from Unity Technologies to run it.