How do I find a history app of recently used icons on my v20 android?

[Pam82]

Hello so I have this V20 android from Sprint and I want to check which apps were recently opened on my phone. E.g. if my photo gallery, text message or other apps was opened. I want to know if my boyfriend opened my phone up. I have to leave my phone open without a password becuase our 2 year old son kept getting my phone and calling the emergency line (911) so I have to keep it open. Please help. Thanks.