1. What do you mean by notional share and how did you arise at 1/24th share for your sister?
After the property was acquired by your father, it became his own and absolute proeprty.
Upon your father reported to have died intestate, all his properties shall devolve equally on all his legal heirs, since you are 6 children to your father, your sister by virtue of one of the legal heirs shall exercise equal rights at par with her siblings.
This is not ancestral property, hence there is no question of amended law of the year 2005 to operate in this situation.
2. Dont stretch your imagination, you may read the provisions of law properly before taking any hasty steps.
3. This will be decided by court, if there is no amicable solution arrived among yourselves on this.
4. Preliminary decree shall confirm her rights in the property, she is not bound to accept your terms if she do not like or willing, she may go by the court order and the court may decide about all such eventualities as per law. It is not necessary for the court to accept your offer or the court shall force her to accept the offer given by you.
5. If you are aggrieved by the pre-decree, you may have to prefer an appeal before the appellate court on the grounds you may rely upon.