Lots of great free apps out there to try! Some with more ads than others, but fun to play with.
Yes, on Zero!
Zero Calories is nice and simple.
I like the tracking tools on Fasting Hours Tracker (green fork, knife, spoon icon) and Fasting Tracker (red fork icon).
LIFE also has additional community learning and support groups that you can join.
I am sure there are plenty more suggestions!