Yes. You must get all the flight tests and your license, CPL or ATPL, issued within 36 months.
If you do the ATPL theory and get a CPL IR issued then the ATPL theory is frozen until you have enough hours to get an ATPL issued.
If you just do the CPL, and don't bother with the IR, the ATPL theory credit disappears in a puff of smoke after 36 months and, if you ever wanted an ATPL, you would have to do all the exams again.