An iPhone's functionality is restricted in Lockdown Mode. While basic communication features like calls and texts continue to work, most message attachments are blocked except for certain images, videos, and audios. Some functions within apps, such as links and link previews, won't be available. Browsing via Safari might be impacted due to the blocking of certain web technologies, potentially causing slower loading or malfunctions on some sites. Specific Apple services like FaceTime, Live Photos, and iCloud Photo Sharing are disabled, and shared photo albums are removed. Additionally, the iPhone won't automatically join non-secure Wi-Fi networks in Lockdown Mode.