How to delete group chats on iPhone 13 that are more than an hour old

You can only select them one by one for deletion.

Open WeChat, the chat history will show the time, swipe right to delete or click to enter, select delete and exit.

SMS messages can be quickly deleted: Open iPhone "Settings" - "Messages" - "Retention Messages", and select "30 days" or "1 year" in this interface, then if it is more than one month or one year information will be automatically deleted. Or use gestures to delete, open the information interface, hold down a message with two fingers and slide down to select in batches. After confirming that it needs to be deleted, click the "Delete" button in the lower right corner.