Since iOS 13 you've had the option to use Sign in with Apple to register with any apps, websites or services that offer it. Basically it is like signing up for something using your Google or Facebook credentials, but it doesn't track and profile you like they do. If you have been using Sign in with Apple you can view and manage which of your apps and services are using it in your iPhone or iPad Settings. Here's how:
There are several ways to check if someone else has used your iPhone or has access to your iCloud account. If there's any reason to suspect that an unauthorized person has used your device, or if you need to make sure that nobody else has access to your iPhone, start here. Taking the steps below can determine whether or not anyone besides you can sign into your account, see your location, or browse your personal information.
Location services on the iPhone is constantly collecting and tracking the position of your device anywhere in the world. For most people this provides an incredible level of convenience for everyday activities, such as looking at maps or connecting with friends and family. On the flip side, there can be a dark side for privacy when it comes to personal data being shared.
iOS 14 has changed and improved its message filtering in the Messages app. Filtering lets you separate messages from known and unknown senders into separate lists. For example when you get a message from an unknown number, or a PIN sent from a website for two-factor authentication, or a political message or just flat out spam, these messages will be separated from the ones from your contacts, making for a less cluttered message list that is easier to navigate. This feature is off by default so you will have to enable it to use it.