There is a single triangle icon in the top left corner of the front face. There is a double triangle icon in the top left corner of the back face.
The converted mana cost of a modal double-faced card is based on the characteristics of the face that’s being considered. On the stack and battlefield, consider whichever face is up. In all other zones, consider only the front face. This is different than how the converted mana cost of a transforming double-faced card is determined.
In the Commander variant, a double-faced card’s color identity is determined by the mana costs and mana symbols in the rules text of both faces combined. If either face has a color indicator or basic land type, those are also considered.
If an effect puts a double-faced card onto the battlefield, it enters with its front face up. If that front face can’t be put onto the battlefield, it doesn’t enter the battlefield.
If an effect allows you to play a specific modal double-faced card, you may cast it as a spell or play it as a land, as determined by which face you choose to play. If an effect allows you to cast (rather than “play”) a specific modal double-faced card, you can’t play it as a land.