Can we be great finance specialists without having ACCA/CPA?

Sure you can, but only if you master the CPA or ACCA program by you own. The qualification itself is just a test and many people are passing it without understanding what many elements shall mean. The huge weakness of finacials is that they can't easly understand the nature of the components of the financial statements neither the related tax matters, this is why you have to aquire the required knowledges in those2 qualifications programs.

Yes you can, you just need to continue learning. There are many books and online course that you can do to improve your knowledge.

In my opinion without good qualification you can not become a great accountant.