1.5 kg tub of grout and adhesive for 12 tiles (tile size 6inc/4inc

A few factors will determine if one tube will be enough or if you need two: - Size of the area being tiled - 12 tiles for a small wall/shower area is likely doable with one tube, but a larger wall may need two tubes. - Thickness of the adhesive/grout lines - Thicker applications or grout lines will use more product. - Wastage - There is always some wastage as you learn to use the products. More wastage means needing more product. - Type of tile/backer material - Some more porous surfaces absorb more adhesive. In general, for a small 12 tile wall/shower area with thinset and standard 1/8" grout lines, one tube of adhesive and one bag/tube of grout should suffice. But it's always a good idea to have extra on hand just in case. As for the rusty metal - it would be best to try to remove it if possible. Rust can contaminate the adhesive over time and cause tiles to de-bond from the wall. Try scraping/sanding it off or cutting out that small section of wall board/backer and patching. If you can't fully remove it, applying a rust inhibiting primer before tiling may help, but removal is preferred. I would not want to rely on just tiling over the rust long term.

Yes will be enough

Shut be inaf