Effects that modify the creature’s power or toughness (such as the effect of Giant Growth) will apply no matter when they started to take effect. The same is true for counters that change its power or toughness (such as +1/+1 counters).

You can use any kind of sticker to cover the cracks in Astroquarium’s art, not just art stickers. Name, ability, and power and toughness stickers will function no matter where they are physically positioned.

After the activated ability resolves, the creature will not retain any of its previous colors or creature types—it will be only a blue Shark or a blue Octopus. Its other card types (such as artifact) and supertypes (such as legendary), if any, will remain unchanged.

Once the activated ability resolves, it doesn’t matter what happens to Astroquarium or its . . . um . . . cracks. If the creature becomes a 4/4 Shark and then the cracks become completely covered later in the turn, the creature won’t spontaneously become an 8/8 Octopus.