Hello. Is it possible to spawn particles for example inside a cube and kill them if they touch the borders? Thanks
Depends on what you mean. You could certainly make a particle emitter and place it (or them) inside anything you like. Do you mean 'emit in a cube shape'? If so, you could use a Mesh Emitter and assign a cube mesh to it. And you can have a smaller cube that emits into a larger cube that kills.
As for killing particles, I'd guess you'd want to look into World Particle Collider (http://unity3d.com/support/documentation/Components/class-WorldParticleCollider.html). Worst case, you'd have to script your own particle system (or get one from a scripter).