Q3: How to generate $e^+e^-\rightarrow \gamma /Z \rightarrow \mu ^+\mu ^-$ using Pythia with JSF

The process $e^+e^-\rightarrow \gamma/Z$ using Pythia are included in Pythia. To set parameters to run this process, do

  $ run jsf gui.C 
% $

This will open JSF control panel. Then set parameters as follows;

 
[Controls] ->  [Generator Parameters...] -> 
	       [Pythia ...] -> [Event Type] -> gamma/Z

Decay mode of Z can be also restriced only to mu-pair as follows.

 
[Controls] -> [Generator Parameters...] -> 
	      [Pythia ...] -> [Event Type] -> Z decay mode

and specify 13.