Which of these can be considered lock-in strategies?

This is correct. Once you have decided to buy the Nintendo GameCube with the corresponding games changing the gaming system would mean that you even have to buy new game discs to play these games. Hence, you are locked-in to the Nintendo gaming system.

This is correct. When using a loyalty program and collecting points, you are in fact locked-in to this airline because you would lose all the benefits and the status associated with your collected miles. So, changing to another airline would mean that you have to start collecting miles all over again.

This is also true. Similar to the case of airline loyalty programs discussed in the lecture, the described pricing scheme also locks-in consumers. So, if you have already bought 7 coffees at Starbucks, you get a free coffee after purchasing another 2 coffees. Switching to another supplier would mean that you have to buy 9 coffees to get a free coffee.