Step 1: Since now you have target’s phone number, call on his/her iPhone – starting a FaceTime call will also do it.
Step 2: Now, targets iPhone screen will show a message icon, just click on ‘Message icon’ and then ‘Custom Message’ to go to the New Message screen where you are allowed to type a reply.
Step 3: Next, you need to activate Siri by long-pressing the Home button and say “Turn on Voice Over,” and Siri will get the job done by turning it ON.
Step 4: Go back to the message screen and double tap the bar where you are required to enter the caller’s name and then hold, while immediately click on the keyboard. This may not succeed in the first time, so repeat this step until you see a slide-in effect on the iPhone’s screen above the keyboard.
Step 5: Now, ask Siri to “Turn off VoiceOver,” come back to messages and simply type in the first letter of a caller’s name in the top bar, tap ⓘ icon next to it, and then create a new contact.
Step 6: Next, you can select add photo and choose a photo. Yes, now you are in and can look at the victim’s photo gallery just like you are browsing the phone, even though the iPhone is still in the locked state.
Step 7: You can select any contact on the iPhone, and you would be able to see all previous conversations of the target with that contact.
I will be making a video as a follow up.