The deceased cannot see us when we visit their grave, there is no authentic hadith or verse to establish that. About the deceased being able to hear us there are two opinions. First one says that they can hear us and the second says that they cannot hear us.
You can have a heart to heart with the deceased but you should not be making dua to them. Although making dua for them is permissible.
Shaykh Navaid Aziz answers and explains....
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