THis mixture is formed in the course of inorganic qualitative analysis for Hg(I) detection (1:1 molar ratio)
HgNH2Cl is a covalent compound.
For reaction with aqua regia write down separate reactions for Hg and HgNH2Cl and balance them. Of course, you can dissociate HCl and HNO3, but they are needed for balancing reaction
Hg + HCl + HNO3 = H2HgCl4 + NO + H2O
HgNH2Cl + ... = H2HgCl4 + NO + H2O + N2