It would be alot easier to answer your questions if you gave more detail?
I can only assume you are the principal applicant and living in Canada with your sponsor and doing and outland spousal PR application?
Question #15 You need to put the address where you are currently living, that is the address CIC will use to mail you any correspondence.
Question #24 and 25 If you have an address in Canada obviously you are visiting your spouse, you need to say yes and put the dates you have been in Canada, show your passport stamps, flight tickets etc to verify this.
If your sponsor has visited you in your country, you need to do the same thing. Put the dates he visited you and copies of his passport stamps and if available his airline tickets.
Question #28 If you have an address in Canada I assume you are living with your spouse, so you answer YES.
Question #30 Most outland spousal applications, the Canadian goes to the principal applicants country, they marry there and the sponsor returns to Canada to work. Most sponsors, especially if they are sponsoring a spouse from a third world country supply some sort of financial support, they prove this with copies of Western Union receipts, money transfer receipts to joint accounts etc.
If you are living with your spouse in Canada you simply explain what your financial arrangement is. Perhaps your sponsor gives you a certain amount of money each month and you are responsible for certain bills etc. Or if hes lucky your are independentely wealthy and give him a certain amount of money

Not sure if I answered all your questions, it would be interesting and helpful to know your situation in more detail.
Hope this helps somewhat,
Regards,
Raymond.