A:AnswerYes you can as long as they are the 4K cameras. Each camera systems use different base stations and cannot be interchanged. I do believe there is a limit to the number you can add. I just uploaded a review of these cameras. You may want to read before buying the 4K system.
A:AnswerYou can setup the Arlo Ultra to record when there is motion, audio or both. Additionally, you may purchase a CVR (continuous video recording) plan that records all the action 24/7. Learn more about CVR here: http://bit.ly/33QYZzD. ^KN
A:AnswerEverything you said depends on the details related to your question - but if you're upgrading, you most likely are going to Ultra cameras which automatically allows for 10 cameras and gives you 1 yr on the higher end plan for free.
A:AnswerThe Arlo Ultra camera is not backwards compatible with older generation Arlo base stations. At this time, you cannot sync an Arlo Ultra camera with a base station other than the Arlo SmartHub.
If you are referring to the Arlo HD Wire-Free Camera, this camera is backward compatible to the Arlo SmartHub.