Since and for:
To mean point of time since is used
I have been working since 2012.
He had been reading in this college since last year.
They have been playing football since morning.
To mean space of time for is used.
I have been waiting for you for two hours.
They had been waiting for you for one hour.
He has been reading the story for five hours.
Between and among:
To mean two persons or things in one between is used.
I divided the mangos between the two boys.
He ordered to give the fruit between these two girls.
To mean more than two persons or things among is used.
I divided fifty taka among ten boys.
Can you tell who the best among us is?
By and with:
If the work is done by any agent ‘by’ is used.
The work was done by the boy.
He was taught by this teacher.
If the work is done with an instrument ‘with’ is used.
I write with a pen.
He did the work with the help of these tools.
We killed the snake with this stick.