I understand that it is debated if the Universe started from zero entropy or not.
Does that mean:
A. The Universe had a temperature at t=0, but we are not sure if it was 0
or
B. We do not know that a metric like temperature applies to the universe at t=0 ?
We don’t even know if the Universe had a t=0. And if it did, we know nothing at all about what conditions were like at that moment.
After about 380 000 years, the temperature dropped below 3 000 K.
After about 10^-43 s (Planck era) the temperature was about 10^32 K.
since the evolution is roughly Temp = 1/square root (time)… well if time is =0 then Temp = infinite 
! ! ! ! Naked Singularity 
!
So we can ponder the temperature shortly after the Big Bang, but not exactly at t=0. And as Chronos said, t=0 is a tricky question…