For each chosen mode, perform that mode in its entirety before continuing on to the next chosen mode in the order printed.

You can't choose a mode more than once.

In a Two-Headed Giant game, Rankle's second mode causes each team to lose 1 life twice.

As the third mode is performed, first the player whose turn it chooses a creature they control, then each other player in turn order does the same, knowing the choices made before them. Then all the chosen creatures are sacrificed at the same time.

As the first mode is performed, first the player whose turn it is chooses a card in hand without revealing it, then each other player in turn order does the same. Then all the chosen cards are discarded at the same time.

You can choose a mode even if some or all players will be unaffected.

If you really want, you can choose zero modes for Rankle's triggered ability, but carefully consider the hidden costs in not entertaining someone titled Master of Pranks.