It depends which interactive game you join. If you're talking about Pottermore, then no, you fill in a questionaire and are sorted based on your answers.
Harry Potter played for Gryffindor house.
harry potter and the goblet of fire
The badger represents Hufflepuff house in the Harry Potter series.
harry's parent's house
There is a House Elf and his name is Dobby.
No, James Potter was in Gryffindor house. Harry's mother was also in Gryffindor.
dobby from harry potter
Slytherin.
Harry particulary hates Slytherin.
Harry Potter plays on the Gryffindor Quidditch team.
By 'you' you mean Harry Potter and his friends? The very first one.
To be the best Harry Potter cosplayer, be sure to wear robes in your favorite house and to have a wand.