On the game reserve where I was staying we went out for three hour game drives in a four wheel drive truck which had seats mounted in the bed. There was a cover overhead to block the sun but the truck was open on the sides. In theory, anything could have jumped in though the animals stay back because they see the truck as a monolithic large creature that is too big to attack.
The Rhino’s horn has been cut to prevent poachers from killing it for its horn. It is believed consumption of Rhino horns will result in their extinction soon.