To play a focus card, do you have to perform the instructions? For instance, I have controlled spaces all around my cities, don't need to put any more control tokens down, but I have a culture focus card in the 5th slot which states I need to place control tokes. Can I ignore this and play the card anyway or is it stuck there in the 5th slot until I can create a new city, etc., to have new spaces in which to play control tokens?

The answer is on P15 under Focus Cards, Focus Row and Tech Dial: A player can resolve a focus card for no effect.