How can I see my login information

To check if someone has logged into your iPhone or if there's suspicious activity on your device, you can follow a few steps. Unfortunately, iPhones don’t provide a direct log of when the device is accessed like a traditional computer would, but here are some ways to review any unauthorized access and steps to stop it:

• Review any unauthorized device access to your Apple ID: Go to Settings > Tap your name at the top > Scroll down to see all the devices signed in with your Apple ID. If you see an unfamiliar device, it might indicate unauthorized access.
• Check for unusual iCloud activity: Use a web browse, and log into your Apple ID @ iCloud.com. Review your recent login attempts (you’ll be notified if there was any unauthorized login attempt from another location).
• If you suspect someone else has your credentials, immediately change your Apple ID password. Settings > Tap your name > Password & Security > Change Password.
• Enable two-factor authentication if it isn’t already on to add an extra layer of security.
• Check Apps for Unusual Activity: Go to Settings > Privacy > Review apps that have access to your data, location, camera, etc. If you see anything unfamiliar, remove its access.
• Check the Screen Time settings: If someone set up Screen Time restrictions on your phone without your consent, go to Settings > Screen Time and review or disable restrictions.
• As a "last ditch effort," enable "Lockdown Mode." This is an advanced security feature in iOS 16 or later that restricts certain phone functionalities to protect against attacks. Go to Settings > Privacy & Security > Lockdown Mode to enable it. Ref: About Lockdown Mode - Apple Support

And just as an add-on to Tesserax's useful suggestions, no one can log into your iPhone remotely. The only way someone can use your iPhone is if they have it in their hands. So if the iPhone has never been out of your possession, or if it has but you have a passcode on it that you have not told to anyone else, no one else can have logged into it.

Your accounts, such as iCloud, are of course a different matter. See Tessearax's information on how to address that.

Regards.