You can choose the name of any card. You can't choose the name of a token unless it's also the name of a card.

Some cards can have alternative names, such as split cards, adventurer cards, double-faced cards, and so on. You may choose one of the two names the card can have; Disruptor Flute's abilities won't affect anything with the other name. For example, if you choose Ondu Knotmaster, Throw a Line will still cost only {W}{B} to cast.

To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.

If you name a card that has both a mana ability and another activated ability, the mana ability can be activated but the other ability can't be activated.

Activated abilities contain a colon. They're generally written "[Cost]: [Effect]." Some keywords are activated abilities and will have colons in their reminder text. An activated mana ability is one that produces mana as it resolves, not one that costs mana to activate.