Open TMJ surgery can help reposition a disc displaced anteriourly without reduction? Will it last this procedure? Thank you very much

Maybe. Oms's have done TMJ surgery to reposition the disc for years with varying results. Most oms's agree that the indication for TMJ surgery is loss of function with or without pain. The key requrement being loss of function.
Maybe. This surgery repositions the disc, but unless the reason the disc displaced in the first place is determined and rectified, it probably won't last!
Sometimes. A displaced disc without reduction may improve spontaneously. If you need surgery, usually arthroscopic surgery will work - much smaller procedure. If open surgery required, results are usually permanent.