Infinite level

namaste, this is too general. try forum.unity3d

be sure to search on here on terms like "random" "instantiate" "infinite" "move" etc you will find many, many answers about it on here

Hopefully its pretty obvious, but its impossible to generate an "infinite" level. You will have to fake it to some level, since memory is finite.

What you probably want is procedural generation, which will generate the level as the player "discovers" it. You can make the world predefined if you set the seed for the random number generator you use for creating the level.

This is how old-school games such as Elite made their massive game-worlds/universes.