Below is a list of gestures that can be used on the iPhone when VoiceOver is active:

Tap: Speak item.

Flick right or left: Select the next or previous item.

Flick up or down: Depends on the Rotor Control setting.
To change the rotor control setting touch with two fingers and move one finger up while the other finger moves down (like turning a knob).

Two-finger tap: Stop speaking the current item.

Two-finger flick up: Read all from the top of the screen.

Two-finger flick down: Read all from the current position.

Two-finger triple tap: Open the Item Chooser.

Three-finger flick up or down: Scroll one page at a time.

Three-finger flick right or left: Go to the next or previous page (such as the Home screen, Stocks, or Safari).

Three-finger tap: Speak additional information, such as position within a list or whether text is selected.

Double-tap: Activate the selected item.

Split-tap: An alternative to selecting an item and double-tapping is to touch an item with one finger, then tap the screen with another to activate an item.
Touch an item with one finger, tap the screen with another finger (“split-tapping”): Activate the item.

Double-tap and hold (1 second) + standard gesture: Use a standard gesture.
The double-tap and hold gesture tells iPhone to interpret the subsequent gesture as standard. For example, you can double-tap and hold, then without lifting your finger, drag your finger to slide a switch.

Two-finger double-tap: Answer or end a call. Play or pause in Music, Videos, YouTube, Voice Memos, or Photos. Take a photo (Camera). Start or pause recording in Camera or Voice Memos. Start or stop the stopwatch.

Two-finger triple-tap: Open the Item Chooser.

Three-finger double-tap: Mute or unmute VoiceOver.

Three-finger triple-tap: Toggle the screen curtain on/off.