The correct IUPAC name of [Co(NH3)4(H2O)Cl]Cl2 is:

🧠 Three Ligands, One Sort

For $[\mathrm{Co(NH_3)_4(H_2O)Cl}]^{2+}$ the three ligand stems are ammine, aqua, chlorido. Two start with 'a', so resolve them by the second letter: ammine (i) vs aqua (u) → ammine wins. Final order: ammine → aqua → chlorido.

🗺️ Wire Up the Name

Ligands & multipliers.

• 4 × ammine → "tetraammine"
• 1 × aqua → "aqua"
• 1 × chlorido → "chlorido"

Oxidation state of Co. $x + 4(0) + 0 + (-1) = +2 \Rightarrow x = +3$. So Co(III).

Counter-ion. Two outer chlorides → "chloride" (no "di" before chloride in modern IUPAC).

Stitch: tetraammineaquachloridocobalt(III) chloride — option (2).

⚡ The Alphabet Filter

Run a strict A–Z scan on ligand stems first. Most JEE distractors put either chlorido before aqua (option 1) or aqua before ammine (option 4). Both fail the alphabet filter immediately.

⚠️ No "Dichloride" or "Trichloride" Outside the Bracket

The post-2005 IUPAC rule omits multipliers on outer counter-ions when their charge is implied by the cation's oxidation state. So "chloride" (not "dichloride") even when there are two outer Cl⁻. Option (3) drops chlorido entirely — wrong because it's an inside-bracket ligand.

$\boxed{\text{Answer: (2) Tetraammineaquachloridocobalt(III) chloride}}$