According to the law of reflection,

when two waves meet, they reflect
when two waves meet, they interfere
when a wave meets a boundary, the angle of the reflected wave is equal to the angle of the incident wave
when a wave meets a boundary, the angle of the refracted wave will be equal to the angle of the incident wave

  distance on the y-axis and time on the x-axis.

explanation:

the instantaneous velocity = change in position/time taken

the slope of the graph should give instantaneous velocity.

  slope of a graph = change in value of y -axis / change in values of x -axis

  comparing both the equations

    change in value of y -axis = change in position

  change in values of x -axis = time taken

so position values should be on the y axis and time values should be on the x axis.

distance on the y-axis and time on the x-axis.

because growing process had stoped after 4-5 year