First, you need to find a university and apply for admission in a course you want to study. To apply for a university in Canada you need to take any of the language proficiency tests and GMAT/GRE. Based on these scores, the universities will decide whether to select or not select your application.

Yes, you can do. Its not a big deal but try for achieving more bands as you will get more options to go for many other countries. If you scored high band then you will be have multiple options for choosing country according to your choice.  Even if you want to go for Australia then you need to score 6.5 overall bands as the cost of study in Australia is compatible to students.

Yes, you can but you need to score minimum 6.5 overall in IELTS to go for study in Australia and 5.5 for London. Even every country has its own band capability to bring you there. Your English must be fluent. Try for grab high bands. If you achieve more than 6 then you will achieve more options to study in abroad.