Is zakat due annually on the principal of the saved money along with its increase, or on the principal of the money only? Are gifts coming from abroad for family and friends counted as part of zakat on money? Is it permissible to give zakat on money to one's parents?

Zakat (definition) is obligatory on wealth whenever a year has passed over it and it reaches the nisab (definition), even if zakat was paid on it before. Zakat is obligatory on the entire wealth, not just the newly acquired part. There are rules and conditions for giving zakat as a gift. It is not permissible to give zakat to one's parents.