Hi,
Here is a link to the user guide for your clock/radio.
https://www.manualslib.com/manual/75813/Ihome-Ih8.html#manual.
Try operating the Alarm On / Off button and see if this stops the alarm. (beeping)
Here is a link to the relevant page in the manual. See the using the Alarms section halfway down the page.
https://www.manualslib.com/manual/75813/Ihome-Ih8.html?page=5#manual.
Also the batteries are there only to maintain the clock and the alarm settings in the event of a power failure. They cannot run the radio. You need to have the adapter plugged in all the time. There is a battery indicator icon in the display that shows when the batteries are low and need to be replaced.
Hopefully this is of some help.