Short answers, pulled from the story.
The Nazi regime began systematic persecution of Roma people in 1936 when they established the Racial Hygiene and Demographic Biology Research Unit. This unit conducted fieldwork to study the Gypsy question and provided data for formulating a new Reich Gypsy law.
At least 19,000 of the 23,000 Roma sent to Auschwitz were murdered there between 1942 and 1945. The SS liquidated the remaining 2,898 inmates on the 2nd of August 1944 after a resistance attempt by prisoners.
Heinrich Himmler ordered that Romani candidates for extermination should be transferred from ghettos to the extermination facilities of Auschwitz-Birkenau on the 16th of December 1942. This order mandated the deportation of all Roma over the age of six living in occupied territories.
Bulgaria and Finland did not cooperate with the Porajmos just as they did not cooperate with the anti-Jewish Shoah. Romania deported between 28,000 and 33,000 Romani people under the Hungarian Arrow Cross government while Denmark and Greece had no recorded cases of Roma killed.
The United States Holocaust Memorial Museum estimates that just 285,650 Roma people were killed by the Nazis in Germany Axis countries and occupied territories. New findings reveal that the Roma death toll was at least about 200,000 to 500,000 of the 1 or 2 million Roma in Europe.