Achieve to - Is this word used correctly

Dear all,

I am mentioning a sentence:

To monitor the tasks delegated by CEO to ensure that the task is achieved to agreed deadlines.

Can we replace "to" with either "on" or "before". Is the use of "to" in the above sentence right?

Thanks
Rajan

It's not a sentence as it has no main verb.

As an aim or objective, it would sound better as

"To monitor the tasks delegated by the CEO to ensure that they are completed by agreed deadlines."

(Tasks are not achieved.)

Rover