How do I transfer data and files from old dead iPhone 12 to new iPhone 14?

Regarding your data if the iPhone is dead and you want to transfer the data to a newer device…

1. If you have an iCloud or iTunes latest backup, then there is nothing to worry about. Just restore from it, else...
2. If You have synced your data to iCloud, then what you will get back is what you have synced to iCloud and uploaded to iCloud Drive;
   1. The information that is synced and stored in iCloud, like Contacts, Calendars, Bookmarks, Mail*, Notes, Voice Memos, Messages*, shared photos, iCloud Photos*, Health data*, call history*, and files* you store in iCloud Drive.
   2. *-If you had turned on Messages in iCloud, iCloud Photos, Mail, Health data, call history under iCloud, and files you store in iCloud Drive your content is automatically stored in iCloud and is available on all devices that use the same Apple ID
3. You have imported your Photos & Videos to Mac/PC then they are safely residing there on Mac/PC
4. You have uploaded some of it to Cloud Drives using the Files app (iCloud Drive, Google Drive, OneDrive, DropBox, Flickr, box, AmazonDrive, Adobe Creative Cloud etc). The data remains there.
5. If you have not backed up or do not have the latest backup, nor imported nor you have synced or uploaded your data to cloud drives prior to the situation that you are in, then I am sorry, all your data is lost.