This chemical formula is for ammonium acetate.
NH4CH3COO is ammonium acetate.
ammonium acetate
yes
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.