No In and Out Burgers are not Halal.
They only serve beef burgers, w/or w/o onion and cheese, lettuce, pickle side packets of salt.I do not see anything on there about it being Halal or kosher so I doubt they are, unfortunately. I'm not sure many places in the US are Halal, not many are even Kosher.
Doubt it, you can consider mashbooh.
Thanks! Your answer is awaiting moderation.