The iPAD solution is certified by the vendor; these employ a PCI P2PE certified terminal and a PA-DSS certified PoS software on the device. The software enforces security controls on the device as well as performs checks such as root/jailbreak detection, iOS patch level, security/passcode settings etc. and if any of these do not match what the vendor specifies (which is what they certified) it won’t work.

As for the terminals on older PoS as long as the PED is certified and the PoS is certitied its not a problem.