Identify the nature of the compound

The formula is $\mathrm{GaAlCl_4}$.
This is best written as an ionic salt: $\mathrm{Ga^+[AlCl_4]^-}$

because $\mathrm{AlCl_3}$ is a Lewis acid and can accept $\mathrm{Cl^-}$ to form: $\mathrm{[AlCl_4]^-}$

Gallium is more electronegative than aluminium, so in such mixed halide systems it tends to form the cationic part, while aluminium forms the anionic tetrahalido complex.

Analyse the anion $\mathrm{[AlCl_4]^-}$

In $\mathrm{[AlCl_4]^-}$, aluminium is bonded to four chlorine atoms.

Oxidation state of Al: $x + 4(-1) = -1$ $x - 4 = -1$ $x = +3$

So the anion is tetrahedral $\mathrm{[AlCl_4]^-}$.

Determine the oxidation state of Ga

Since the whole compound is neutral: $\mathrm{Ga^+ + [AlCl_4]^- \rightarrow GaAlCl_4}$

Hence oxidation state of Ga is: $+1$ not $+3$.

Check each option

Option A: $\mathrm{Cl}$ forms bond with both $\mathrm{Al}$ and $\mathrm{Ga}$ in $\mathrm{GaAlCl_4}$
This is false. In the ionic description $\mathrm{Ga^+[AlCl_4]^-}$, chlorine is coordinated to Al, not to Ga.

Option B: Oxidation state of $\mathrm{Ga}$ in the salt $\mathrm{GaAlCl_4}$ is $+3$
This is false. As shown above, Ga is $+1$.

Option C: $\mathrm{Ga}$ is coordinated with $\mathrm{Cl}$ in $\mathrm{GaAlCl_4}$
This is false. The coordinated chlorides are around Al in $\mathrm{[AlCl_4]^-}$.

Option D: $\mathrm{Ga}$ is more electronegative than $\mathrm{Al}$ and is present as a cationic part of the salt $\mathrm{GaAlCl_4}$
This is true.

Final answer

The correct option is: $\boxed{\text{D}}$