1.a. If it is found that the requisite court fee was not paid then you may be directed by the court to make good the Deficit court fee.
You should understand the difference between court fee and the stamp duty, if court finds you that you are required to pay deficit court fee, you have to either pay it or your suit may be dismissed for the same reason.
2. You do not have to answer their such illegal and unlawful questions or allegations because once they accepted that it was an unregistered partition deed, then the said deed becomes invalid in the eyes of law, therefore the partition itself can be held as illegal and invalid. However even if it was a registered partition deed, since you being one of the shareholders, if you are excluded from the partition and allotment of your legitimate share in the property that were partitioned, you can claim your rightful share in the property through court of law.
3. You do not have to challenge the recitals mad in the 1970 deed. The properties subsequently discovered and found to be the family property, then you have full rights to claim your rightful share in them.
Do not get misguided by any false or misguiding information in this regard, which may be spread to dissuade your claim in the property.
4. You can mention that the sale done by the brothers which include your share in the property hence it is not binding on you therefore you are not required to pay stamp duty on them, however as far as the partition suit is concerned you may have to pay the court fee to the newly added property as per the court fee and suit valuation act of your state.
5. The mere mention of constructive possession will take care of all the issues.