One and you only need to enter the front face
February 20, 2021 10:12 p.m.
Worth mentioning, like as with split cards such as Breaking / Entering , the color identity is all symbols included - not just the side you "intend" to use.
So the color identity of a MDFC is that of all colored mana symbols that appear on both sides, not just the front. That is important for if you want to use a card such as Jorn, God of Winter Flip. He is Sultai, not mono-Green.
February 20, 2021 11:03 p.m.
In that way, it is the same as transforming cards, such as how Archangel Avacyn Flip is Boros and not monowhite, as her reverse side, Avacyn, the Purifier is denoted to have a red identity, acknowledged by the red circle next to her typeline as well as the coloring of the card's border.