in a Pokemon center somewhere.
Friendship
The friendship app or frenship checker is given to you by a girl on the first floor of the Eterna city Pokemon center.
You need to get it's friendship to full.
you need about 40 to 50 hearts for max friendship
find a Chancey, and then get it to max friendship and level it up
give it the oval stone when it has high friendship
from Riley he gives you a Riolu egg and you can evolve it at high friendship
yes two big hearts
you have to level up at a high friendship level.
It will evolve when you raise it's friendship. Then lvl it up once.
You can find the app in the Pokemon Center in Eterna City. Talk to one of the girls.
you cant... you have to make chansey evolve with high friendship. you can find chansy on rout 209 in diamond, pearl, and platinum