Is it permissible to give bank interest to a sick, widowed mother or to a married sister whose husband is of modest means, with the intention of getting rid of it, in addition to giving them private money? And is female circumcision still a religious obligation nowadays?

Female circumcision is recommendable. It is not permissible to dispose of usurious benefits by giving them to one's mother, unless she is poor, because she is among those whose maintenance is obligatory upon you. As for relatives whose maintenance is not obligatory upon you, there is no harm in giving it to them as long as they are poor.