Hi
Welcome to the forum. Your questions are good questions!
Just confirming you are talking about this trigger:
http://marketfeeder.co.uk/solutions/green-up-hedge/either-direction-greenup/If you refer to the attached screenshot you will see a constant: minutes before the off to start betting. If you change the value from 15 to whatever minutes you want and save and reload the trigger file, that takes care of your first question.
The trigger is already pre-programmed to trade just the favourite. You will see I have highlighted this in the initial bets trigger.
The rest of the triggers in the file will operate only on the selection initially bet on, so you should have nothing further to change.
Hope you will enjoy working with the triggers.