sites that compares air fares & price fluctuations of budget airlines

I'm booking a ticket from Singapore to Manila (around 3rd week Oct '17)
& return ticket (1st week of Nov '17)

Q1:
I once saw a site that compares various airlines fares but lost it:
anyone have it?

Q2:
I've noticed it's not necessarily the longest away the airfare is cheapest for
budget airlines : any way that public can see which dates are the cheapest
say a few months in advance?