There is no such thing as NH4Ci
NH4Cl (with a lowercase L) is ammonium chloride
Nonexistamine. If it did exist, the best name for it would probably be ammonium carbide, but that particular combination of atoms has loose bonds dangling ... it might theoretically exist as an ion or free radical, though a double or triple free radical (depending on exactly how the hydrogens are arranged) is massively unlikely. HCN and NH2CH3 are both real compounds called hydrogen cyanide (or cyanic acid) and aminomethane respectively.
The formula for ammonium carbide is (NH4)2C. This compound consists of two ammonium ions (NH4+) and one carbide ion (C2-). The carbide ion is formed from carbon and has a 2- charge, while the ammonium ion is a positively charged polyatomic ion composed of one nitrogen atom and four hydrogen atoms.