The advantages and disadvantages of ACCA have been mentioned below with all the specific points you have mentioned.
The difficulty level for ACCA is quite high after the initial few examinations. However, with the correct approach and right guidance, it can be relatively manageable.
The usefulness can be broken into professional and personal life. If you take it up as a profession and enter the field of finance, ACCA can provide you with a great start to your career. If not, an in depth knowledge of finance and accounting will be useful in all your future endeavours (such as personal finance, financial management, tax, etc.)
Career opportunities are huge if you would like to enter the field of accounting and finance. Being a global qualification, you could secure a job in any of the 180+ countries recognising this. In India, majority of the ACCA members across the country are employed in either the Big 4 or an MNC. However, not all of these countries allow ACCAs to practice as they would have their own Chartered Accounting body. So it would depend on your future plans. Countries such as UK, most countries of the EU, UAE, etc. allow ACCA members to practice.
The process is very simple. You can register online in a matter of minutes, register for your exams online, study for the same by yourself or with tuition providers, and appear for exams. You would need relevant 3 years of experience, and a few modules to complete.
The duration would be approximately 3 years