How can I see if someone read my message on my iphone

If the person receiving your iMessage has Send Read Receipts turned on in Settings > Messages you will get a notice when the text is read below your bubble. If they have not done this you will not get any such information. This does not work for SMS texts.

You cannot. If someone else has access to your device, you’d have to ask them. The device has no way of knowing who is using it. Anyone with your screen passcode and access to your device uses that device the same as you do.

If someone has your AppleID and password, they can also access your iMessages as you would.

I understood what you meant and answered you.