Let me make this very clear here, the "delivered" and "Read <time>" signs will not appear if your number is blocked by the recipient.
BUT BUT BUT...
Not getting "delivered" and "Read <time>" is not an indication that the recipient has blocked your number. There are other circumstances when you will not receive those signs. Some of them are...
At the recipient's end...
- Phone not in the network coverage area
- WiFi is not connected to the Internet - ISP (Internet Service Provider)
- Data plan exhausted / not enabled
- The device is switched off.
- The Phone number is changed
- The device is in Airplane Mode.
- iMessage is deactivated.
- The phone number is de-registered from iMessage
- Travelling abroad
Other causes are...
I tested Blocking / Unblocking of a contact for iMessages (Same is not valid for SMS/MMS). Please see the pic below which is self-explanatory
