What are the differences between "وَمَا أَنْتَ بِمُسْمِعٍ مَنْ فِي الْقُبُورِ" (and you cannot make those in the graves hear) and "وَمَا أَنْتَ بِمُسْمِعِ مَنْ فِي الْقُبُورِ" (and you cannot make those in the graves hear), and what effect does the tanwin or its omission have on the word?

Reading "وَمَا أَنْتَ بِمُسْمِعٍ مَنْ فِي الْقُبُورِ" without tanween is shadhdh (anomalous) and not among the mutawatir (concurrently transmitted) readings. The idafah (genitive construction) in grammar, such as "Zayd daribu 'Amrin" (Zayd is a striker of Amr), is called a verbal idafah because it lightens pronunciation, and it may have semantic benefits. If a participle is used transitively (i'mal) and not in idafah, it denotes only the present and future. However, if it is in idafah, it can denote the past, present, and future. I'mal indicates an event and its proximity to the verb, while idafah leans more towards nominality, and its expression is probabilistic, potentially bearing more than one meaning, unlike i'mal, which is considered a definitive expression. This difference in connotation is clear in examples like "This is harisun al-madrasata" (This is one who guards the school) and "This is harisu al-madrasati" (This is the school's guard).