How to check if iPhone 6 is jailbroken and reveal malicious apps?
My friend's iPhone 6 seems to have been compromised and I would like to know how I can be sure. I connected her phone to iTunes and checked for installed apps, but they were all harmless. Previously the same guy "hacked" my mom's iPhone 5 and I found TeamViewer and other apps that can be used for spying on her iPhone 5; however, I couldn't find Cydia so I need another sure way to determine if an iPhone 6 is jailbroken. I already updated her iOS, but still need to find out.
The guy seemed to have read her Messenger and BBM conversations. I scanned her PC (basic scan with MalwareBytes), but there was nothing, so he's probably been monitoring her phone's screen just like he did with my mom's a long time ago. I don't think he has her password because I never saw her log in at suspicious times (times where she usually doesn't log in). I also checked her facebook log-in history and nothing seemed suspicious, but I presume you can delete activities from your log-in log.
Summary of my question:
1- What is a sure way to determine if an iPhone 6 is jailbroken?
2- Is there a chance that the jailbreak is hanging around even after updating the iOS?
3- How can I reveal possibly hidden apps on iPhone 6 (jailbroken or not)? Particularly apps like TeamViewer on a jailbroken iPhone 6?
4- Is there another external way of intercepting Messenger and BBM messages? For example, by monitoring her net traffic? I'm basically asking if BBM and Messenger packets are encrypted.
Thanks in advance
iPhone 6