I bought one of these toilet bowl blue cleaners attached to a plastic clip that hangs on the lip of the toilet bowl. This is on a new toilet and the flush water flow was so strong it flushed it down the toilet . The toilet flushes ok but tends to back up a little if paper is flushed.
How do I get it out ?

I'd say that if you can't reach it with your hand or someone with really small hands can't reach it either, then you need to remove the toilet from the floor and get it from the bottom.

I would try a toilet auger before taking the toilet off the floor. I have had great success clearing out things like you have by attaching a triple fishing hook on about 2' of line. Hold the end of the line and flush the hook down. Wait until the flush action stops and slowly pull out the hook.

If it is still inside the bowl, I would remove the toilet, flip it upside down, and removed it by hand. You don't really want the cleaner to enter your sewer pipe and get lodged somewhere down the pipe. Then you would have a bigger, and more costly, problem

Milo