Hi,
The purpose of Notice period is to find a better replacement and smooth handing over. In your case, Replacement is in place, handing over is completed and you are also ready to buyout the notice of 30 days which is fair on your part. I could not find no logic in holding you back.
Lets see what you can do Now:
a. Just try escalate this to the next level in HR / Management of your present company and see whether any good thing is happening for you. If you have already done this and you could not see anything positively, try with the following..
b. Please speak to the HR of the new organization where you are going to join in and try to make understand on the issues.
c. Your current company can hold only the experience & Relieving orders if you leave without completing 90 days and not anything else. They cannot even touch any statutory payments to be made to you. - In fact, as per the appointment order, it is clear that you can buyout the notice in case of inability to serve the notice.
d. Hence Please try to understand whether your new company will accept you without experience & relieving order. - If they are okay without experience & relieving order, you can proceed further to join your new company.
e. If you decided to leave as indicated in "C", send out en e-mail to your present company in detail on the reason for your improper leaving as per their present company policy. This may help in further.
Though the experience & Relieving orders are important in future when go up in your career, this is the only option you have now to go ahead with.
Regards,
Kannan M