Is the wife entitled to claim her maintenance and the maintenance of her children for the past 6 years, given that the husband did not inquire about them or spend on them throughout this period?

A husband is not permitted to refrain from spending on his wife and children. The wife has the right to demand her past maintenance if she has not waived it; otherwise, she should take her case to court. As for the past maintenance of children, it is forfeited by the passage of time according to the majority of scholars, unless the mother intended to claim back from the husband what she spent, or if a judge decreed it, according to the Maliki school.