1) You can use an optical delay or an initial delay. There is also an Optical Ring Controller which will control how many times the signal propagates in the ring.
2) Yes the signal index changes which iteration of the loop you are investigating.
3) Not exactly the case every time for every project. You can check to see how many iterations it takes for the first output to arrive at the Power Splitter and then every iteration after that will be one loop. In this case I am getting the 0th iteration arriving at the output, so yes the iteration corresponds to the number of loops. In some cases, like using an Initial Delay this might be different.