All cards are playable: To play a card, you only need to pay its cost. If you can not perform one or more of the effects of the card, then just perform the ones you can. Some examples below:
Mangrove: You must place a forest tile next to an ocean tile. If you can not do that, then you can not place the tile at all, the oxygen is therefore not raised, and you therefore do not gain VP for this.
Urbanized Area: If you can not place this city next to another city, then you can not place this city at all, and you therefore get no VP.
IF: When playing a card where it says you gain something IF something is fulfilled, then this can only be counted once. For example Peninsula: you gain 2 blue dice if you place a forest next to an ocean tile. If you place this forest next to 2 oceans, you still only get 2 blue dice. (Swamp, Peninsula, Immigrant City, Mohole Lake, Tipping Point, Lakefront Resorts).
Lakefront Resorts (promo): If you place a tile next to an ocean, you gain 2 yellow dice. If that tile is adjacent to more than one ocean, you still only get 2 yellow dice.
Manutech (promo): When you play a green gard, you also immediately gain what is indicated in the brown production box on that card.
Tharsis Republic: when revealing this corporation, place a city tile on the gameboard and gain its 2 VP and placement bonus.
Terralabs (promo): During production turn, when you draw cards up to 5, you draw up to 7 instead.
Vitor (promo): You gain a yellow resource of your choice when playing a card with VP (red ribbons). Playing a card with negative VP will not give you this bonus, and playing a card with more than 1 VP will still only give you 1 yellow resource.
Capital (promo): Gives 2 VP for being a city, and 1 VP per adjacent forest, plus 1 VP per adjacent ocean tile.
Equatorial Magnetizer: All tiles on the middle row counts, for a maximum of 7 green dice.
Fertile Fields: Yes, it raises oxygen 2 times.
Infrastructure: Gain and roll a grey dice for each city tile on the board.
Mohole Lake: If you place this ocean tile next to a forest or city, you gain 2 extra VP, making a total of 4 VP (regardless of the number of the number of forests or cities).
Tipping Point: Raise temperature or oxygen and gain VP for that. IF you also got a bonus from the track, you gain 2 extra VP (4% oxygen, 10%oxygen, -24ºC, -16ºC, 0ºC).
Commercial District: Rotate up to 3 of your resources.
Decomposers: Spend any green resource to gain a plant and 1 immediate VP
Development Center: Spend any amount of science resources to gain that amount of other resources of your choice from the dice pool.
Electro Catapult: Gain and roll (do not rotate!) any 3 dice of your choice from the dice pool.
Industrial Microbes: Gain a grey resource of your choice (steel/titanium/city).
Lobbying: Spend any yellow resource to gain and roll any dice and recieve 1 immediate VP.
Restricted Area: Discard 2 cards from hand to gain 2 immediate VP.
Robotic Workforce: Pay 1 steel resource during an action turn, to get 1 extra main action after your normal main action.
Coordinator: Immediately gives you a whole extra turn (production turn or action turn).
Efficient: Take a free support action any time during your turn (production turn or action turn).