Absolutely. It was possible to trigger the mic/camera on older Macbooks without turning on the green LED. This led to people being spied on without their knowledge (by script kiddies, not nation-states). More recently, there's the unlocking of the San Bernardino shooters' iPhones.

Literally every model of iPhone ever released has been "jailbroken" if that's what you mean. Including of course multiple re-jailbreaks per model when Apple patched the original exploits.

There's an argument that the secure enclave is unhackable, although there have still been ways around it up until very recently (is it finally 100% secure or have the new exploits just not been discovered yet?)

I prefer to work on the assumption that no hardware / software can ever be 100% secure.