How to answer any OC-05 NEET question systematically:

Step 1 — Identify the substrate class:

Is -OH on aromatic ring? → Phenol → EAS reactions, high acidity
Is -OH on sp3 carbon? → Alcohol → classify as 1°/2°/3°
Is it R-O-R'? → Ether → Williamson synthesis or HI cleavage

Step 2 — Identify the reagent:

PCC (anhydrous) → Mild oxidation → 1° stops at aldehyde, 2° → ketone, 3° → no reaction
$KMnO_{4}$/$K_{2}Cr_{2}O_{7}$ → Strong oxidation → 1° → carboxylic acid, 2° → ketone
$ZnCl_{2}$/conc. HCl → Lucas test → turbidity time tells alcohol type
conc. $H_{2}SO_{4}$, heat → Dehydration → Saytzeff alkene (3° > 2° > 1°)
$CO_{2}$/NaOH/pressure → Kolbe → carboxylation at ortho → salicylic acid
$CHCl_{3}$/NaOH → Reimer-Tiemann → formylation at ortho → salicylaldehyde
$Br_{2}$/$H_{2}O$ → Phenol bromination → 2,4,6-tribromophenol (no catalyst)
$RO^{-}$$Na^{+}$ + R'X → Williamson → ether (only works if R'X = 1°)
Excess HI → Ether cleavage → both fragments become iodides

Step 3 — Apply the selectivity rule:

If multiple positions possible → use Saytzeff (alkenes) or o/p-directing (-OH)
If competing SN2/E2 → 1° halide → SN2; 2°/3° halide with strong base → E2

Step 4 — Check the answer:

Is it consistent with known pKa ordering?
Is the reaction mechanism consistent with substrate and conditions?