yes you can a lot!
soak with water until it softens and thegently scrape
You don't need to seal ceramic tiles if you use epoxy grout you will be fine with the high traffic
Granite
Sealer is applied on top of the glaze & does not penetrate the glass Glaze, so over time & with use & cleaning it will wear off. so YES!
Yes, but you should you use an adhesive that is ductile
It all depends on the sealer you used! I use a product called StableCrete that penetrates into the grout joints to waterproof them without leaving a film. Ready for light traffic in four hours. The Grout is what you seal with a ceramic install and not the ceramic!
yes
Yes, if the adhesive is smooth, no lumps and if you use a compatible glue, not thinset cement
To remove a paving sealer on floor tiles, use a basic scraper with a razor blade. Make sure the blade is flat against the tile when scraping.
Yes, you can (but there are many cheaper ways of doing it , such as regular tile glue)
Sweep it, use a Swiffer Dry, or a stone cleaner. Do not use regular floor/tile cleaners and do not use a great deal or water.