secret of 1st pack/box

Does all who buy first pack get a 100% exo from it. Same with box someone say that 1st box always give you a legendary card. Someone can tell is it true or not?
My first pack give me a exo. And now I'm trying to collect gold for box to check 100% chance to get legendary.

 

Pretty much luck I think.

 

I didn't got a exo in my first pack

 

U just ruin my big plan to flood game with a ton of new account to farm 1st pack.

 

lol i just did buy a first pack and no exo lol

 

Luck of the draw

 

no le in my first box