What exactly is required for platinum god?

What is needed to achieve platinum god, I know it's pick up all items and complete all secrets but, when I search in if all marks are needed I get contradictory answers saying you only need all marks on the lost for true platinum god but only need a single moms heart kill on the rest

But if you need all secrets wouldn't you have to do lamb and blue baby on each character too?

I'm just a bit confused on what is actually required TwT