TPS23754: question for TPS23754

hi, team

   I have some question for TPS23754 ,

(1) In the electronic characteristic page of TPS23754 , the VC UVLO is 15V ,

      but in the operation condition VC is 12V , and the transformer's bias coil is 12V,

      I don't know the mean of  "UVLO" , why operation voltage could be  under "UVLO"?

(2) In the slvrb41b.pdf , because the flyback transformer is too expensive,

     this total BOM is too much compared to the slvu304c schematic even if the total component counts is less.

    Do you have other Alternative materials to use on the slverb41b structure?

    Or maybe please provide the 1st and 2nd inductance and turn ratio range to us  in the slvrb41b so that we can search it.

(3) Do you have the documents for calculating and choosing 1st and 2nd inductance and turn ratio for the TPS32754?

     I am interesting in calculating that.

 thanks very much.

slvu304c.pdf

slvrb41b.pdf