In the far future tutorial I put plant food on the middle tile and activated the other 2 tiles. If I put plant food on another tile will it still work the same way?
No, it doesn't matter. Plant Food will activate all tiles connected to the tile on which you use it, regardless of where they are positioned or which one you activate first. Connected tiles are the ones marked with the same symbol.
The tile receiving Plant Food first will be activated immediately. The remaining connected tiles will activate (simultaneously) after the original tile deactivates.