Who appointed titles and power to the boyars

When Ivan IV came to power in 1547, much more of the boyar's independent political power became obsolete. The independence and autonomy experienced by the princes of the regions in Russia was abolished under Ivan IV by the end of the sixteenth century, making them “the prince’s sons”, or just simple boyars serving the Grand Prince.

corrupt also means cruel

the correct answer is the following is a list of inventions made in the medieval islamic world, especially during the "islamic golden age" (8th to 13th centuries),[1][2] as well as the late medieval period, especially in the emirate of granada and the ottoman empire.

science and technology in the islamic world adopted and preserved knowledge and technologies from contemporary and earlier civilizations, including persia, india, china, and greece-roman antiquity, while making a number of improvements and innovations.