Can these cables be daisy-chained, and if so, what is the maximum number of cables?

I have not tested these for daisy-chaining them, but with other simular (these are better built) I have done 2. I personally do not go beyond that. If you need to go longer, I would consider USB over Cat5 adapters (not internet.. the adapters just use Cat5 cable) OR better yet.. Move the equipment in question.

Does this extention work properly with a USB mic connected to a computer?

If the USB mic relies on its power source coming from the USB, then it is quite possible it WON'T work with this cable. This cable is intended for data only.

Can you connect two of these cables together to get to 64'?

Dear Customer, Thank you for your interest in our USB 2.0 Repeater/Extender cable. You can connect 2 of these cables to get 64 feet. We would also like to remind you that this cable is used for data only and not for charging.Please contact us at service@bluerigger.com if you have any additional questions. Thanks, BlueRigger LLCservice@bluerigger.com

Will this work to extend a charging cable for an arlo ultra 2 security camera to supply continuous power to the battery in the camera.

No - the BlueRigger USB extension active/repeater cable does not charge devices; the charging pin is inactive on this cable. For more questions or concerns, please visit us on our website or on our Facebook page.