Well I have programmed in Quick Basic, and now learning C++. What I need to know is can I develop a game on a windows system then compile to Linux?

Game will be linux exclusive.
Game is a very basic isometric sprite game, possibly drawn whole backgrounds (as in no tiles, just a painted picture).
The most technical aspect will probably be collision detection.

I have seen Allegro, but unsure if this is suitable. I know there is openGL but this perhaps a little advanced.

Simple answer: yes.

More advanced answer: yes, mostly, with a little work and perseverance.

Final answer: your code can be 100% portable. Your code is about 80% of what you need to write to get something up and running. The build environment, packaging paradigms, and various scaffoldings are radically different on the two platforms. Expect bumps along the way. Keep in mind it has been done, and it is possible.

If you're writing a Linux-exclusive game (assuming you mean GNU/Linux, not Android/Linux), you are probably just better off writing on Linux.

Simple answer: yes.

More advanced answer: yes, mostly, with a little work and perseverance.

Final answer: your code can be 100% portable. Your code is about 80% of what you need to write to get something up and running. The build environment, packaging paradigms, and various scaffoldings are radically different on the two platforms. Expect bumps along the way. Keep in mind it has been done, and it is possible.

If you're writing a Linux-exclusive game (assuming you mean GNU/Linux, not Android/Linux), you are probably just better off writing on Linux.

Awesome thank you. Yes as soon as I'm able I will be installing linux (escaping windows can never be done quick enough ;)