You have many options to find out the block. If you do not see the DP of the contact, then it means that they have blocked you. However, there may be a mistake in this. Many times you remove the contact DP, then it is not necessary that you have been blocked. But after being blocked, you do not even see the status of the contact. If you are not seeing both the things then it means that you have been blocked.
Along with this, you can also know by sending a message to the user that you have not been blocked. If your message is getting delivered then it means that you have not been blocked. But if your message is not getting delivered then it means that you may be blocked. In case of block, even your message will not be delivered. But such a situation is not going to happen every time.
How to Unblock?
If you want to unblock someone, then for this you have to follow the whole process. Because you cannot unblock yourself by going to someone else’s account. For this, you have to request the front user only. You can unblock only if he wants. Apart from this there is no other option. To be unblocked, they can go to their block list and remove your name.