Making a rangoli is a physical change as the colours can again be brought to their powdery form.
Burning a candle is both a physical as well as a chemical change as the wax can be again moulded to a candle but the wick burns when lighted giving off soot and smoke.
Burning of a cracker is a chemical change as it involves a chemical reaction when lit up.
Preparation of sweets is a chemical change as cooking leads to changes in the chemical composition of the ingredients.