I can only think of one real "chain opp" that's ever come up for me - the Celebrity opportunity "Best Food In Town". As soon as you eat at the restaurant, you immediately get another call telling you to talk up the restaurant to three sims. You don't get the reward for completing the opp until you do that, and the opportunity name doesn't change.
The omni plant series opportunities all build on each other, but they don't follow one right on top of the other, and you get a "completion" message after completing each one. Those definitely count as three opps - but are the two halves of "Best Food In Town" one opp or two?