? Can Longteng and Sigma 24-70mm lenses be put on Canon 5D3? What's the difference with the original factory?

No problem, as long as the bayonets are consistent.

The difference between the original factory and the deputy factory is that the original factory has better workmanship, technology and materials.

The most important thing is that the optical design of the lens is different. The original factory has some unique patented technologies, while the deputy factories are generally worse.

The advantage of the deputy factory is that it is cheap, so you can consider the deputy director. Some deputy factory directors are in danger of losing focus.