new install

So I am thinking of putting a free-standing wood burner on the ground level of my two story house. I have no basement. I am planning on running the chimney up through the inside of the house, passing through the ceiling of the first story then the floor of the second story then the ceiling of the second story then out the roof, for a total of about 18 ft I have a coulpe of questions. What is a safe distance I can place the chimney away from the walls I have read 9-10 inches, as I will probably frame in the part that is on the second story, as it will pass through my closet. Also what is a safe distance the ceiling and floor can be cut away for around the chimney I have read 2-3 inches? Any thoughs would be helpfull thanks in advance. also would it be wise to frame in the part that is in the attic to help it stay warm. planning on using at least double wall insulated pipe.

what is considered class "a" double wall??? i am assuming... also what do you mean by enclosing the part in the closet witha "chase"? i was planning on just buiilding a wall around it with 2 x 4 and drywall keeping the proper clearance of cours.. thanks for your help. what your thoughts about inclosing the part in the attic?

would it be possible to run the class a chimney pipe just where it passes through floors & walls rather then running it the entire 16' (which i dont think i could afford at 100.00 for a 3' section)???? for example run class a through the first level ceiling and floor then switch to double wall keeping the 6" clearance in my closet which is 8' high then switch back to class a for the remaining 6-8 ft? or would that be silly?

thanks for all your help one last question..i think.. will i need to use a ceiling support box on both of my ceilings? of course i will on the lower level but will i need to in the closet where it will not be seen or can i use some sort of flasing or something on the inside of the attick? to keep the cold from the attick from going into the closet area.;