Been making yogurt at home for years. I just heat milk to the point when it's just about to boil over. Never measured the actual temperature, but I'm pretty sure it's less than 100C. I just cool it until it's warm to touch (about 40-45C) before adding the culture (a spoonful of last day's yogurt), then leave it overnight in the oven with the pilot light on.
My first job was in Infosys back in 2001. Coming from a lower-middle class farming family, it was a huge deal. My monthly gross was something my dad (farmer) + mom (school teacher) would earn in an entire year. I remember my dad proudly putting a portrait of NR Narayana Murthy (founder of Infosys) on our wall - it is usually reserved for gods/ancestors or revered sages.