For starter tile, if you are in a corner, cut the long edge off, otherwise the jagged edge overlaps the ends of the next tile (right side fits edges on left side). They link together. 

Yes they are suitable for apartments, they are super sticky. To remove with no or minimal paint damage, use a hair blower to soften the glue. But definitely ask permission from the landlord because there may be some damage after removing. Or you can just repaint the wall. It is an improvement to the kitchen for sure!

Yes, it can stick well on wallpaper, make sure the wallpaper is clean, no grease. They are very sticky even on decorative paneling.

We cook daily and I have tea twice a day from stove top kettle. No issues at all. Definitely can withstand the steam and from cooking. Gas range. Grease wipes right off when fresh, with paper towels. If hardened it comes off easily with a spray on cleaner.

Yes it would. I'd recommend coupling the product with additional adhesive and a caulking along the borders, just for extra security, or put clear silicone on the outside edges so water couldn't get behind them.