If the application form clearly asks questions like "have you been ever arrested/prosecuted/bound down/fined by court/any pending case". Going by the details you have shared, when you were booked under 304A (IPC, I assume, which deals with "Causing death by negligence" and you were prosecuted in the same case, maybe fined as well
and you are not mentioning the case which is still being heard and is pending, all of these will be equivalent to concealment of material facts and information and that may lead to cancellation of appointment at a later stage due to suppression of facts\candidate information through self-disclosure. Further, Central Government jobs involve intense background checks including Police Verification and verification of Court records, hence this case will come up at some time sooner or later.
If you are certain that you will get acquitted, I would suggest, disclosing these details will give you a fair chance to defend any rejection on this ground that the case was disposed of and you were acquitted and freed from all charges. This will be a better path than your appointment getting canceled due to you not disclosing the facts.
Let me answer the remaining questions as well
1) whether to disclose in details in joining form or not?--Already expressed my opinion
2) Can they cancel appointment letter? Or deny me job ---Ideally for cases where you were acquitted or found not guilty or non criminal cases. government jobs aren't denied
3) what is impact of this case on my appointment? ---None as long as you are acquitted
4) why are asking five year residence addresses with police station name ? ---That is a standard procedure to verify Police and domicile records. Police verifies any criminal record in places where you have stayed for 6 months or more.
All the best!