Step 1: Keeping molecularity and order separate in your head.
Molecularity is a theoretical idea, it counts how many reacting particles must collide together in a single elementary step, and this number is fixed once you know the mechanism. Order, on the other hand, is measured experimentally from how the rate actually responds to concentration changes, so the two ideas answer different questions.
Step 2: Checking the claim about molecularity being an experimental quantity.
Since molecularity comes purely from writing down the elementary step, not from a lab measurement, calling it an experimental quantity is incorrect.
Step 3: Checking the claim about complex reactions.
A complex reaction is really a sequence of several elementary steps, and each individual step has its own molecularity. But there is no single molecularity you can assign to the overall balanced equation of a multi-step reaction, so the statement that molecularity has no meaning for complex reactions as a whole is correct.
Step 4: Checking the remaining two claims.
Molecularity counts actual colliding particles, so it can never be zero or a fraction, it is always a positive whole number, and having four or more molecules collide at exactly the same instant is so improbable that molecularity values above three are essentially never seen. \[ \boxed{\text{For complex reactions molecularity has no meaning}} \]