the recipient can read your message without you knowing. The recipient will get your message in a ‘request’ form. They have choice to accept or decline it.
- If they decline your message request, then you will never know if the recipient has read your message or not.
- If they accept your message request, then you can easily know as explained in Scenario #1.
So, you can easily know whether your sent message has been read by the recipient or not. But, you can not know the exact time when it was actually read. Hope, maybe in future, Instagram will launch this feature also.