how can an international student change course

[dufferdexter]

I went through the threads and found a few posts about changing course but none of them gives a clear answer..

1) can a person change course before entering Canada ( of course after getting visa ) ?

2) how can he change course which starts in different intake ? ( i know about the rule that if student doesn't maintain full time student status for more than 90 days after getting study permit , his/ her study permit will become invalid)