1. If you are eligible to appear in Indian Civil Services, i.e., if you hold a Graduation degree and you have not yet crossed the upper age limit (for your category), you can appear in the Civil Services examination even while working in any other organization.
2. You have to apply through proper channel (with an advance copy sent to UPSC) to receive No Objection Certificate (NOC). NOC is required at the time of interview. After selection, you have to submit technical resignation/resignation to join new position.
3. What is bond? If you undergo training with salary, then the organization which is imparting the training, will ask you to execute a bond to ensure working in the said organization for 3/5 years after the training. However, if both the organizations (where you are working and where you will work in future) are under Central Government, then there is a provision of transfer of bond, provided you apply for the new post through proper channel. I can cite my own example in this regard. I executed a 5-year bond with Eastern Railway as I had undergone an eleven-month training with full salary. After completion of training, I joined duty. After around 1 and a half years, I joined Central Secretariat in New Delhi. As both organizations are under Central Government and I had applied through proper channel, my bond was transferred to Central Secretariat with the condition of compulsory working under Central Government for another 3 and a half years (I already spent 1 and a half years in Eastern Railway).
4. Bond amount: The bond amount is the total salary drawn during the training period and interest on the salary @12.5% p.a.
Beware! I question everything and everybody.