Using tell to launch a clone of another sprite is quite a useful technique (that @jens ) suggested to me for a project but I've been having issues with it.
I've finally worked out why and thought it could be useful information to others in future.
I've made a simple demo
which works fine with a wait 2 secs delay inside the loop
But if you reduce that down to 0.5 secs - it doesn't work in the way that's expected
and that's because of two issues.
The first one is that the loop is looping around faster than the the launched clone can deal with its speed.
So by the time a clone gets to say the number i - the for loop is already on its next pass and so it gets the wrong value
And even worse, the last clone is getting the number 4 - and that is down to the fact that, in Snap!, a for loop variable is increased until its gone past the last value.
Things change again if delay is 0 secs
and with no delay at all - even the sprite position goes wrong
There is a cure for all this though and that is to click on the launch block black arrow and expand it to give "with inputs"
or the more explicit method when you want to feed in more than one parameter
Anyway - hope this helps someone else - I'm off to apply it to my Missile Command project 