Physics HELP! PLEASE HELP!!!

I have a few physics questions, could you please show me how you get the answer and show me what equation you use? Thank you sooo much in advance!
Free- fall equations(no friction)
1) A common flea is recorded to have jumped as high as 21 cm. Assuming the jump is straight-up, with what initial velocity would the flea have to jump to reach this height?
2) Erica throws a ball straight up with a velocity of 9.98 m/s. How fast is the ball moving when it has traveled 4.88 meters?
3) Tianna tosses a ball straight up with a velocity of 32 m/s. a) calculate how long it takes for the ball to reach its maximum height. b) calculate the maximum height.
4) When some volcanoes erupt, big rocks have been measured to shoot upward with speeds up to 1000 m/s. Find the height those rocks can reach.
5) An air-balloon is rising at a constant speed of 1 m/s. Liz accidently drops her pen and 10 seconds later it hits the ground. how high was the balloon when she dropped her pen?

{ Take g = 10 m / s^2 , [upwards as + ve] }
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* Applicable equations of motion for the above questions *

I) DeltaY = Vi * t + 0.5 * g * t
II) Vf ^ 2 = Vi ^ 2 + 2 * g * s
III) Vf = Vi + g * t
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Question 1 :

DeltaY = 21 cm ( 0.21 m)
g = -10 m /s^2
Vf = 0 m/s [ * At maximum height, flea motion is zero * ] - A

From eqn II :
0^2 = Vi^2 + 2 * (-10) * 0.21
Vi = +/-Sqrt(4.2)

==> Vi = 2.05 m/s upwards [ positive motion - upwards ]

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Question 2:

From eqn II :
Vf = sqrt [ (9.98)^2 + 2 * (-10) *4.88 ]
= 1.40 m/s upwards

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Question 3: