Question

why do you think that scientist or engineers have not cross the earth crust your provide approve give short answer​

Answer 1

YES scientist or engineers have not crossed the Earth's crust as the temperature inside is around 1000°C at the base of the crust, around 3500°C at the base of the mantle, and around 5,000°C at Earth's centre. The temperature gradient within the lithosphere (upper 100 km) is quite variable depending on the tectonic setting.

AND it would require a lot of energy and resources to do so, which will be of no use. On the top of that it would also damage the environment.