Recordable Talking Button for Dog with Led Function and Sounds Answer Buzzers, Orange+Blue+Green+Pink (4pcs)

Spec description says 2 aaa batteries required but not included and under the "product information" it states batteries are not required. which is it?

Can these be heard across a classroom?

How many seconds can one of them record?

Are they easy to depress? I’m training my dog who is only 5 pounds.