(since you asked for basic understanding only, I am not including actual calculations. Please let me know in the comments section if you wish to verify your solution(s))
For (b): Use the formula for distance (s) made during an accelerated motion:
with v_0 and s_0 being the initial velocity and distance, both 0 in this case, and with "a" denoting the acceleration, in this case solely due to gravitational acceleration so: "g."
You are given the distance made, namely 10 m, and the duration t (0.88s) and so using the formula above you can solve for g.
For (c), to determine the final velocity at time 0.88s use the formula for the instantaneous velocity of an accelerated motion
(velocity at time t) = (acceleration) x (time)
again, with acceleration due to gravity, i.e., a = g and with g as determined under (b).
If my calculation is correct, this mystery planet could be the Jupiter.
