Well, to delete a dynamic sprite, just deactivate it when you want it to go away. It would be something along the lines of
If
>
Left operand: frame
Right operand: 10
Do
Deactivate
Except instead of 10, use the number of frames of animation (that is, the number of frames, times the repeat count of each frame).
To answer your other question, I'd need to know more about how you're creating it, and how many you want to show up.