file size and memory questions

I've been trying to read up on issues relating to file size and memory limits before I get too far gone into my game. I'm still a bit confused by all this though so I was hoping you guys would be able to help me out/clarify a few things?
1. Am I correct in thinking that the size you see at the bottom of the screen when you open your project in GS is the file size?
2. If so, is it also correct that technically there isn't any limit to this size for your project however if you want people to be able to download your game over 3GS then you should keep the file size under 20MB?
3. Finally, when I test the game on my iphone via the viewer what exactly does the memory usage refer to?
What are the safe limits for this memory usage and does the value indicate the memory usage just for that particluar screen being previewed, or for the entire game.
Any help/advice would be great
Thanks
1. Am I correct in thinking that the size you see at the bottom of the screen when you open your project in GS is the file size?
2. If so, is it also correct that technically there isn't any limit to this size for your project however if you want people to be able to download your game over 3GS then you should keep the file size under 20MB?
3. Finally, when I test the game on my iphone via the viewer what exactly does the memory usage refer to?
What are the safe limits for this memory usage and does the value indicate the memory usage just for that particluar screen being previewed, or for the entire game.
Any help/advice would be great
Thanks