I don't think that the HR person would be so foolish to demand a bond amount because if he demands a bond amount, then the entire PIP will become just an intentional one to avoid an employee. The HR should know the consequences that will follow if he demands a bond amount, along with forcing an employee to resign. In fact, no HR can send an email like this where he has asked you to resign.
If your performance has been unsatisfactory, instead of asking you to resign, the HR should have sent a show cause notice informing that the management has decided to terminate you from service, and if you wish to say something, you should make it in writing within, say, three days. When this is the procedure, the HR has emailed that you will be relieved on the 7th and again has asked to submit the paperwork. The second one is a technical error committed by the HR.
But if you feel that soon after submitting the resignation, they will demand a bond amount, then you should take the employer before the law. Therefore, please talk to them. Before that, study what is written in the bond regarding the termination of employment by the employer. If the bond is enforced even when the employer is terminating the contract, then it would be a gainful business for them, that they can hire employees with a bond for two years, and just before that ask the employee to leave on any ground, including bad performance, and then collect a very good amount as a bond! That should not be allowed.
First, the bond itself is illegal, and now in this case, demanding a bond amount when the employer himself is violating the bond. That is not possible. Therefore, speak to the HR person. You should tell him that if he demands a bond amount, it would be against the law, and he will be taken to court.