List all the ways to check that your iphone is not jailbroken?

What I mean is: list all the ways to check that your iphone is not jailbroken in case someone had physical access to your iphone, jailbroken it and then installed a spy software that can also hide the cydia app.

Added (1). yeah I lent my non-jailbroken iphone to someone for a day. I got it back and then had a conversation with a friend with my iphone next to me and then I saw my conversation on twitter. So I think the person I lent my iphone to may have jailbroke my iphone and then installed a spy software (which records and relays sounds) that can hide the cydia app.

Please Help ME! I'm DESPERATE. I want to know if it's my friend who put the conversation on twitter or is it because my iphone is hacked.

Well, if it is, then just reset it and restore from an iCloud or iTunes backup. That will erase the phone. Problem solved and you'll feel less paranoid. Best luck.

Factory reset it then there will be no virus on it.