Do you mind asking the two questions separately?
Which do you prefer to address here?
Will it support one floor or two? What is the joist length on each side? Will it support any ceramic tile? Will it support the attic? What will be the span of the beam?
It will be 40' long and have a post at midspan to span only 20'? There is no 6" steel section that will span 20' supporting 3 floors. I could design a custom shape as an additional service, but no standard shape will even be close.