Hello Bro
Every college has minimum grade requirements at graduation level if you are a graduate in India. GPA points.. but they also consider your work exp. if you have worked and your course. So admission depends college to college.
As for Visa - you just need to justify why this course is relevant, why you chose this course and HOW this education will help you in your life- career wise, financially and how it helps you over Indian education. This is to be written in a letter called SOP - Statement of Purpose.
There are lot of SOP samples you can search on this forum also. Aditionally your IELTS score also governs your Visa approval. Work hard to get a great score. There are tonnes of resources & classes also.
Which agent are you applying through? I had read a bad review on Yahoo Answers - regarding CENTENNIAL that they dont refund fees if your visa is denied. Maybe a one of case, but then it scared me! Be careful of the college you apply to.
Read as much reviews as you can. Agents will push the most high-fee or high-commision earning college or course. I have myself been told a lot of gyan by agents who are only greedy for their OWN benefit. They dont care what happens when you are there! What they get is a commission for each enrollment. They might first push u the highest fees college obviously.
So think twice. Read reviews.Try to connect with students past/new via Linkedin or Facebook Grups