1. جَاءَ عُمَرُ — specific proper name, nominative, no tanwīn.
2. جَاءَ عُمَرٌ آخَرُ — another unspecified bearer of the name, nominative with tanwīn.
3. مَرَرْتُ بِأَحْمَدَ — diptote name, genitive with fatḥah.
4. مَرَرْتُ بِأَحْمَدِكُمْ — muḍāf, genitive with kasrah.
In each sentence identify the governor, case, and cause.