MONDAY

 MODAL VERBS OF OBLIGATION / NECESSITY: 

MUST - inner obligation: you decided what is necessary to do; strict or urgent obligation

HAVE TO - outer obligation: rules, laws; duties or obligation that comes from someone

MUSTN'T - PROHIBITION; NOT ALLOWED, BANNED, FORBIDDEN

You mustn't smoke in public places.

You can't smoke ...

DON'T HAVE TO - not necessary, you decide whether you want to do it or not; it's up to you; your choice

You have to share your homework with me - it's necessary.

You don't have to share, but you can if you want. I'll check it. - your choice

HAD TO - obligation in the Past

I had to wear uniform when I was at school.

DIDN'T HAVE TO - no obligation in the Past

I didn't have to wake up early yesterday as it was Sunday.

Grammar practice: HAVE TO & MUST

                                MUST / HAVE TO (ex. 2)

Speaking with GRAMMAR BASED QUESTIONS: HAVE TO