Vinyl and Linoleum Flooring - replacing carpet on water damaged particle board on porch

I have an enclosed unheated front porch with windows on 3 sides. It is approx. 10'10" X 7'8". The old carpet had holes. There were some boxes/bags that got wet without my knowledge (I believe from summer rain through the screens) and there was some mildew on the carpet under these items. I ripped up the carpet to find, as expected, some water damage and mildew on the particle board subfloor. The front section of the porch floor (front corners and in front of the storm door) have damage: visibly darkener where they got wet, uneven where I assume the water swelled the flooring, and the particle board is even chipping and crumbling in front of the door area. There seems to be an old porch floor under the particle board. I want a solution that is simple and cost effective. I had hoped to cover the entire floor with vinyl flooring and bought 2 rolls of 6' X 9' vinyl flooring at a discount store, very reasonable. I planned to lay the 1 solid 6X9 piece in the front and on the water damaged side, and cover the remaining strip on the side and the entire back with pieces cut from the 2nd roll. In this way there would only be 2 seams (along the edges of the 6X9 piece) instead of multiple seams (if I used the stick on vinyl squares). I have considered sealing the 2 seams with a bead of silicone caulk type product to ensure a waterproof seam. Now my problems: :confused: I feel I need to replace the damaged sections of floor. This is already more cost and work than I planned on. :mad: I think I can handle measuring and cutting the plywood,but my experience and equipment are limited. Can I just replace the damaged front sections with plywood and leave the undamaged sections of particle board there, or do I have to replace the entire floor? Can I use vinyl flooring rolls on the repaired subfloor? Can it withstand temps below freezing? If I can use my vinyl floor rolls, do I have to use adhesive or can I just tack it down on the edges and seams with wide flat head nails or something? (I am not too concerned with appearance, just want it covered in the most waterproof way. I dont' even mind if the edges are not covered with trim. Not like I entertain royalty out there. It is a passageway, sometimes used for plants, and kids' play there on warm rainy Saturdays!) Someone told me the vinyl would not work because it would not expand and contract with the subfloor as the temperatures/humidy changes. They said I had to use indoor/outdoor carpeting. However I would prefer something I can just wipe or mop up (traffic of 3 kids!) Would the vinyl stick on squares be better because they would have seams to allow for some expansion? I am afraid they will allow more chance for water to get to subfloor, and also be more expensive than the rolls I already purchased (which are returnable BTW). ANY advice and information is very much appreciated, ASAP -- it is starting to get cold in New England and I hoped this project would not be this complicated and lengthy!

Welcome to the forums, please you paragraphs. No paragraphs, too hard to read your post but basically it is hard to glue sheet vinyl to old particle board. The top surface just sticks to the sheet vinyl like it was loose saw dust. I have at customers insistence tried sticking vinyl tile to particle board but it just doesn't hold. Sheet vinyl I'm sure would be the same.

I agree with Ray, replace all the old particle board and install a product like Advantech, which is an approved subflooring. You should use an adhesive to hold the vinyl in place. something like Henry's with a serrated applicator would work well.