The time you should be getting is $4.4$ seconds. Something is wrong with the measurements.

On the other hand, in your second and third calculations, you used a very wrong formula to get final velocity.

The relation,$Velocity=\frac{Distance}{Time}$, can only be used when motion in uniform (unaccelerated). But since the body is falling under gravity, the motion is accelerated.

The time you should be getting is $0.4516$ seconds. The measurement is off by $0.05$ seconds. This is reason why you are getting $12.48$ instead of $9.8$. This is one of the cases where even small errors in calculations can give you very wrong answers. Since the time is squared, it will bring more error to the answer.

Moving on, in your second and third calculations, you used a very wrong formula to get final velocity.

The relation,$Velocity=\frac{Distance}{Time}$, can only be used when motion in uniform (unaccelerated). But since the body is falling under gravity, the motion is accelerated.

Therefore, the last two calculations will always give wrong results because the usage of equations is wrong. However, the equations used in first equation are correct.