India

If you think that you are a cabin crew material, you can apply for all the available vacancies with the airlines. If you get selected, they train you in any case. Airlines do not trust on the training acquired from institutions. The only help you get from the institution is that of the interview dates.
In the interview, no airline will ask you any questions about safety, first aid or services because they are airline specific, when it comes to service. But yes, if you are an experienced crew, be ready to answer a few technical ones. In your case they judge you on your personality, grooming, communication and BMI.
To talk about the training, Jet Airways provides one of the best training and that lasts for about 3 months. Therefore, scrap the idea of joining a private institution to be trained on cabin crew attributes and don't waste your money.