Yes, you can come to Quebec to live at any time you like.
If you are targeting to get L/B in the university, you needed to wait for 12 months and have to maintain yourself not to study full time in this first 12 months.
But you can get into the COFI class with no problem at all.
You need to have a lease to prove that you are in Montreal or a resident of Quebec.
2) 如果,我明年九月份入学,能否申请到L/B。
No, not right the way.
You have to stay in Montreal for another 12 months before you can get L/B.
But you can join the French COFI class, you can get $484 per month, totally 10 months.