No - almost always not.
Your hand is much warmer than the table.
When you place an ice cube on a table, the thermal energy will move from the ice cube to the table. Heat will transfer from the ice cube, which is at a lower temperature, to the table, which is at a higher temperature, until both reach thermal equilibrium.
Sugar dissolves faster.
yes
hand
cube
Its called evaporation
Depends on the temperature of the room the table is in. If the temperature is below 32 degrees F then nothing will happen to the ice cube. If above 32 deg, the ice cube will melt. The higher above 32 the temperature is determines how long it will take to melt completely.
Think of it this way. Looking at a cube placed on a table - it has four edges in contact with the table's surface. At each corner of that face, there is a vertical edge rising upwards making eight (with me so far ?). These vertical edges meet the face on the top of the cube (which also has four edges) making 12 in total.
Table salt has a cube structure and table sugar has a hexagonal crystaline structure.
He will need 80 tiles.
It will go in the downward direction, since it melts from there.