Botulinum toxin binds to receptors present at the axon terminal in order to enter the neuron. what vesicular transport process do you think is involved in the toxin entering the neuron

It is the receptor mediated endocytosis process. The botulinum toxin, by binding to a receptor, promotes the creation of a vesicle of endocytosis in the axon terminal incorporating the toxin. The part that connects to the receptor is a heavy chain from the toxin and the part that will further preform the action of the toxin is a lighter chain that will be realised once the toxin is inside the neuron.