CPT

Both the exams have their own importance in their respective field. You can't compare CPT or CLAT because these entrance exam will take you to two different professional courses.
CPT is the entrance exam to become a chartered accountant whereas CLAT is the entrance exam for different careers in legal field.
Thus, decide what you want to do and for further queries feel free to revert back.

After clearing CPT, you can directly register for CS Executive, but if you want to pursue CMA, you need to crack its foundation. If you don't want to give CMA foundation, then you need to clear IPCC and you will be eligible for the exemption of CMA foundation.

I would suggest to go for CPT, then IPCC and you can pursue undergraduate course privately or it will be best to pursue your undergraduate course from IGNOU.
To pursue undergraduate course, and then appearing for IPCC is not a good idea. If you are going for IPCC after your graduation, then you are extending your CA completion time up to 7 years.
ICAI has signed MOU (Memorandum of Understanding) with IGNOU for undergraduate courses, which will ultimately reduce our burden.

ETEN is preferable.