20s are referred to as "target spaces" (rulebook is vague about this) and award beehives.
Anything special with 10s too? they're marked with the same graphical effects as 20s.
Nothing special about them. The 20s are special in that they give a point boost from 15 to 20 (+5 instead of +1) or from 14 to 20 (+6 instead of +2) and they give a +2 point beehive to the first player to reach it and +1 to the next player to reach it. Note that this can't be the same player.
The only other bonus is the red line with the mice. If you cross this you get a new cat token.