Handle code symbolically

Inactive[Join][{1}, Reverse[{2, 4, 3}]]

Inactive[Join][{1}, {3, 4, 2}]

expr = Inactivate[Join[{1}, Reverse[{2, 4, 3}]]]

Inactive[Join][{1}, Inactive[Reverse][{2, 4, 3}]]

expr//InputForm

InputForm[Inactive[Join][{1}, Inactive[Reverse][{2, 4, 3}]]]

expr /. 1 -> 10

Inactive[Join][{10}, Inactive[Reverse][{2, 4, 3}]]

Activate[expr /. 1 -> 10]

{10, 3, 4, 2}