If there is a Supra lock box present, then I have access to the key in the lock box and no one will need to let me in. If there is a code to the lock box, I will need the code to get the key to the property in the lock box. If there is no lock box, then yes, someone will need to let me in.
If there is an alarm, you, the seller, or your realtor will need to give me the alarm code before the inspection.