1)First of all,NH4 is an ion.So you should write it as NH4+.So the equation you wrote is wrong.
NH4+ can be formed by reaction NH3 with any molecule with cation Hydrogen
Eg:NH3+HCl--->NH4+ + Cl-
2)It is wring.The Balanced equation:
H2SO4 + 2 Nh4OH = 2 H2O + (Nh4)2SO4