Hi,
Which question is the correct one:
1. Can I say the same using other words or DO I have to use the same words? OR Can I say the same using other words or I have to use the same words?
Do I need "DO" after "OR"? Yes, in the above example you do.
ie say Can I say this . . . or do I have to . . .
You haven't used the word 'do' in the first clause, so you can't omit it in the second clause.
Compare this.
Do you cook your own meals or do you always eat in restaurants?
You can shorten this to
Do you cook your own meals or always eat in restaurants?
Best wishes, Clive