Installing a 13' l x 12' w x 2' h deck. 6 deck posts will be installed on concrete footings and piers, while the remaining 4 posts would be anchored to an existing 4" think concrete patio slab. Only 3' of the deck will hang over this slab. First, is this allowable or must the slab be removed so footings and piers can be installed? Also, can an expanding foam alternative such as Sika or other backfill brands be used in place of concrete for the posts installed in soil?

I have an upcoming project for our screened in Patio. The slab is roughly 30+ years old and has some cracks on outside perimeter of the slab causing some uneven area's resulting in roughly 1/4" of unevenness some areas slighly more. I'm assuming these cracks were a result of water damage over the years and I've been doing some reading on how to ensure the tiles a lay are even. I've read self leveling products can help level first before leveling. I have little tiling experience and this project will be the largest tiling project thus far at roughly 230 sq.ft. Is there any trick or tips I can use to ensure my tiles come out level aside from self leveling type products? Thanks