The amount of mana you spent to cast Verazol is usually equal to its mana value, normally 2 plus the value chosen for X. However, you also include any additional costs you pay, including the "commander tax" in a Commander game.

If Verazol enters the battlefield without being cast, then no mana was spent to cast it. It enters the battlefield without any +1/+1 counters. If no other effects are increasing its toughness at that time, it will be put into its owner's graveyard as a state-based action.

If another creature enters the battlefield as a copy of Verazol, consider how much mana was spent to cast that creature to determine how many +1/+1 counters it enters with.

Verazol's last ability can copy any kicked spell, not just one with targets.

You can't remove more than two counters as Verazol's last ability resolves to copy the spell more than once. You can't remove just one counter from it if it has only one. If Verazol leaves the battlefield while its last ability is on the stack, you can't remove two +1/+1 counters from it at all.

A copy is created even if the spell that caused Verazol's last ability to trigger has been countered by the time that ability resolves. The copy resolves before the original spell.

The copy will have the same targets as the spell it's copying unless you choose new ones. You may change any number of the targets, including all of them or none of them. The new targets must be legal.

If the spell that's copied is modal (that is, it says "Choose one —" or the like), the copy will have the same mode or modes. You can't choose different ones. This doesn't apply to copying a permanent spell with a modal enters-the-battlefield ability.

For spells with {X} in their mana costs, the copy has the same value of X.

You can't choose to pay any additional costs for the copy. However, effects based on any additional costs that were paid for the original spell are copied as though those same costs were paid for the copy too. Most notably, the copy is also kicked.

The copy is created on the stack, so it's not "cast." Abilities that trigger when a player casts a spell won't trigger.

If a permanent spell is copied, it's put onto the battlefield as a token as the spell resolves rather than putting the copy of the spell onto the battlefield. The rules that apply to a permanent spell becoming a permanent apply to a copy of a spell becoming a token.

The token that a resolving copy of a spell becomes isn't said to have been "created."