Ty for sharing the .cap.
Always nice to see how people make there games,
and without the .cap i would have never found the Bomb to fire.
If you use sounds, then u have to share the sounds together with the .cap
Sounds are, unlike the sprites, not contained in the .cap.
I have not much to comment about the Events. They are pretty straight forward.
Besides that i wonder why you destroy the 2nd boss gun 3 times.
Everything is presented by the right conditions. Line after line.
Although i miss some organizing.
Its a very nice example for how to use particles, they are done very nice.
But about playing the game, or lets say this level, it dont charm me much.
Sorry for beeing honest.
There is no way to escape the boss, or to use strategy in killing it.
But thats of course personal, needless to say i dont like "just click" games much as can be find in "shoot them ups" .
To return to your questions.
1/ No you dont need to set up very big layouts for this. The solution to this you did already. Create the objects outside screen. And call them to the screen on the right moment. Or make different layouts to represent levels, as you did already.
You can warp the stars and bring them to normal speed, dont matter wich solution you go for.
You should name your objects. Anyway. The Ship object is moved by an '8 direction' behavior.
What happens is, you force the ship to move away from the edge of the screen, while the behavior keeps pushing it back to the edge. And that feels like sticking.
So to keep the Ship from moving outside the screen, you have to communicate directly with the "8 direction behavior". Not do things behind its back.
To do this, just place a colider on the right and left of the screen. Make them "solid" in the groups/attributes properties. And the behavior will not intrude those, or put in in other words: keep it on the screen
This for your questions.
Another thing about "waves of objects". The events you build now, mainly control 3 objects and a bunch of particle objects. They are all different objects.
To keep a wave under control, you will need to learn to go along with instances, and the events to control instances.
I wrote about those, towards beginners, from out the eye of a beginner. Well thats what i still am.
You can find them here: search.php?keywords=my+*tuts*%20+%20find
Enjoy constructing. : )