My question is that how can one aqquire/claim the property after fathers death. Law says its automatically inherited , but there must be a process to get that ? like submitting something somewhere ??
Your uncle would not have sold the property by a registered deed, he might have sold the property based on the legal heirship certificate on his name or by creating false and fabricated documents
2) Without any claim , how can my uncle is able to sell the property?
May be with the help of some fake and fabricated documents
3) Can we do something about the land which he has already sold and i think its illegal to sell the property?
Your father has to file a partition suit by mentioning all those properties even the ones already sold
3) how can we get our property step by step?
Your father has to file a partition suit seeking partition and separate possession of his legitimate shares out of his father's properties which are intestate
4) I am grandchildren of my grandfather , my parents are still alive . In this case can grandchild claim the property of their grandfathers property ?? If yes then whats the process of doing that ?
Grandchildren are not entitled to any share in grandfather's property especially when their respective parents are alive.