Hello. The answer to your question is that yes you should pursue B.Com as an undergraduate degree and start preparing for CPT side by side. This will help you focus more and save time.
Also you may do it from Amity if it suits you. But you can also consider doing B.Com as a correspondence course from SOL or IGNOU because Amity requires you to have a certain minimum attendance and then you will have to juggle a lot with coaching for CA.
So it is suggested that you rather go for correspondence. 🙂
There are 3 levels in CA. 1. CPT, 2. IPCC and 3. Final.
Doing bcom before CA would help you in way that you wont have to go through CPT. You can directly go to IPCC and then final!
Doing B.com before CA is going to be very good for you. You would be very focused.
But If you are in 12th or in 1st yr of B.com then why to waste 2-3 years. Start as early as possible. U can become CA in 4&1/2 yrs.
whereas, bcom would make you loose 2-3 years!
PS:- Choose wisely. Do what suits you the best 🙂