What will be the Bar for the person for who took voluntary departure and never leave the country? can the person be able to adjust the status?

The bar will be 10 years for the ones who fail to depart after granted voluntary departure... During that 10 years, the person can not adjust his/her status...

Did you enter legally? Why must you choose voluntary departure?

if you violated your departure before 1996, you have 5 years AOS bar. After 1996 it is 10 yrs bar.

Try to avoid this best you can, if you can not leave you must have to file Motion to reopen
within six months of your VD expirations date.
If somehow you have extended this deadline.
Mark my words!!!
It will not be the most difficulty thing for you
to adjust my status unless immigration laws changes.

My advise to U is do not violate this. If you done so, then send emails to your local politician to support pro-immigration bill, specially the one that will cancel 1996 immigration laws.