The Novice Power, Acolyte Power, and Adept Power feats give you access to a power from the class for which you took a class-specific multiclass feat. That power replaces a power you would normally have from your primary class. When you take one of these power-swap feats, you give up a power of your choice from your primary class and replace it with a power of the same level or lower from the class you have multiclassed in.
Any time you gain a level, you can alter that decision. Effectively, pretend you’re choosing the power-swap feat for the first time at the new level you’ve just gained. You gain back the power that you gave up originally from your primary class, lose the power that you chose from your second class, and make the trade again. You give up a different power from your primary class and replace it with a new power of the same level from your second class. You can’t use power-swap feats to replace powers you gain from your paragon path or epic destiny. If you use retraining to replace a power-swap feat with another feat, you lose any power gained from the power-swap feat and regain a power of the same level from your primary class.
Paragon Multiclassing
If you have the Novice Power, Acolyte Power, and Adept Power feats for a class, you can choose to continue to gain powers from that class rather than take a paragon path. If you choose this option, you gain several benefits.
At 11th level, you can choose to replace one of your at-will powers with an at-will power from your second class. In place of the paragon path encounter power gained at 11th level, you can select any encounter power of 7th level or lower from your second class. In place of the paragon path utility power gained at 12th level, you can select any utility power of 10th level or lower from your second class. In place of the paragon path daily power gained at 20th level, you can select any daily power of 19th level or lower from your second class.