How authentic is the Hadith that mentions the disappearance of humility, the increase of sudden death, earthquakes, and killing (al-harj), the decrease of greetings among Muslims, and boasting about sin in the End of Times, and that these are signs of the Hour's approach?

There is no single hadith that combines all the matters mentioned, but each of them has been reported in separate hadiths:

Removal of Khushu (Devotion/Humility): It is established that the first thing to be removed from knowledge is khushu, to the extent that hardly anyone devoted will be seen. Prevalence of Sudden Death: This has been reported in weak and mursal hadiths, stating that among the signs of the Hour is the prevalence of sudden death. What we see today of the numerous traffic accidents and the like might fall under this category. Increase in Earthquakes and Killing: It is established in Sahih al-Bukhari and Muslim that the Hour will not be established until earthquakes and al-Harj (killing) become frequent. A Muslim Greeting Only Those He Knows: It is established that among the signs of the Hour is "greeting the elite," which means greeting only acquaintances. Boasting About Sins: There is no specific hadith that explicitly mentions boasting about sins. However, a hadith in Sahih al-Bukhari states that some people will consider lawful "al-Hira (fornication), silk, alcohol, and musical instruments." This indicates the legitimization and approval of forbidden actions.