Dear Sahil, Sagar and Karthik,
1. Yes, Industrail training can be beneficial. However, the usefulness in terms of opening of different career options etc totally depends on what sort of work profile is being offered to you during the industrial training.
2. No, your principal cannot deny you the transfer for industrial training. However, as per ICAI regulations, you are required to convey to your principak, your desire to go for industrial training three months in advance.
3. Honestly, delaying an attempt is not a good option. But then what are the guarantees that you will be able to clear the earliest possible attempt? Therefore, you need to rationalize between the desire to learn more during your articleship period and to become CA at the earliest. I personally know many CAs who did industrial training and cleared the finals in the first attempt too!