I am going to Ottawa, Canada

for H1-B visa stamp. Does anyone know if the visa I am getting is a double-entry 6-month valid? Do I have to use one entry when returning to the U.S.? If I don't surrender the I-94 when leaving the U.S. how do they keep track? (I don't think I surrenderred I-94 last Oct when I went to Canada). Also, does anyone know that if I can pick up the visa on the same day?

Help appreciated!!!