Dear querist,
1. You are not entitled to pay the money. If they initiate any legal action against you, an effective defence is the only remedy. You were not trained, they accepted your resignation, they must have provided you the full and final settlement letter. All is in your favour.
2.since they are disputing the fact after your resignation and after full and final settlement. Their averment on the basis of the agreement will be waived considering their acceptance as their admission/acceptance of the terms.
3. no, you are not required to pay the bond. As you have resigned from a proper channel without any departmental violation of the procedure and their acceptance thereof.
4. You can send the legal notice to them as the response to their averments or a mail. A proper drafted reply with all the legal information alongwith a legal opinion is highly recommended.
you can contact me for consultation or on linkedin, in case you need my assistance in the matter.
http://linkedin.com/in/yuganshu-sharma-655091183
regards,
YUGANSHU SHARMA
ADVOCATE