Is it permissible to perform the 'Umrah of Hajj on the night of 'Arafah, then proceed directly to 'Arafah with the pilgrims?

It is permissible to perform Umrah on the eve of Arafah and then proceed directly to Arafah. The reason for this is that going to Mina on the Day of Tarwiyah is a Sunnah, not an obligation. It is recommended for one who performs Umrah to trim their hair and not shave it completely, in order to save the hair for Hajj, so that there remains hair to shave on the Day of Sacrifice.