Short answers, pulled from the story.
The Law for the Restoration of the Professional Civil Service was enacted on the 7th of April 1933, two months after Adolf Hitler came to power and two weeks after the Enabling Act was promulgated.
The law targeted civil servants of non-Aryan descent, particularly those of Jewish origin, as well as members of the Communist Party and political opponents of National Socialism. Its reach extended beyond government to lawyers, doctors, tax consultants, musicians, and notaries.
Hindenburg objected because the original bill by Interior Minister Wilhelm Frick would have dismissed all non-Aryan civil servants immediately. Hindenburg secured exemptions for First World War front-line veterans, those in continuous civil service since the 1st of August 1914, and those who had lost a father or son in combat.
Albert Einstein resigned his position at the Prussian Academy of Sciences and emigrated to the United States before he could be expelled under the law.
Under the First Ordinance issued on the 11th of April 1933, a person was considered non-Aryan if one parent or grandparent was of the Jewish religion. A supplementary decree on the 1st of September 1933 expanded this to include non-Aryan descent established by other means, not solely through religious affiliation.
After Hindenburg died in 1934, the wartime-service exemptions he had negotiated were superseded by the Nuremberg Laws. Jewish civil servants still holding posts under those exemptions were given notice by the 31st of December 1935 at the latest.