Doubt 1: As per the 2005 amendment daughters are not eligible on sharing if their father
died before 2005 amendment came is this understanding is correct.
As per your description the property referred by you may not fall into the category of ancestral nature hence he latest amendment is not applicable to it. Therefore your sisters are entitled a legitimate share as daughter of deceased father and one among his legal heirs or successors in interest.
Doubt 2: Please let me know whether my sisters are eligible on share of my father
property?
Yes as a legal heir to your deceased father, they are very much eligible or entitled to a rightful and legitimate share in your father's property.
Doubt 3: Whether they (my sisters) are eligible on share of my mother’s ancestral properties, and she is willing to give one of the property my sisters
During your mother's lifetime nobody is eligible or entitled to claim any share out of her property, however she may have acquired it. You cannot stop your mother from giving away a portion of her own property to your sisters, you do not have any right over it.
Doubt 4: How can I deal this problem to avoid the sharing to my sisters as they already benefited, they are saying they will go to court.
Solve the problem by talking to them with a reasonable and justified offer to satisfy them and get a registered release deed executed by them relinquishing their rights in the property.
Doubt 5: Do we need to go to court before they filing a suite how can approach
If they dont agree to your proposal or offer they may approach court with a partition suit which has to be contested or defended by you accordingly.
Doubt 5: when both the above laws (1985 and 2005) which one court will be considered 1985 or 2005? or the latest on which 2005 or any other latest amendment came after 2005
Dont break your head on these laws to your subject because neither of the law will be applicable to your current situation