Short answers, pulled from the story.
During the Ottonian period, German kings ruled as Kings of the Franks rather than Romans. This title reflected their claim to inherit the legacy of ancient Rome through the Frankish conquests.
The Golden Bull of 1356 was issued by Emperor Charles IV in the year 1356. It restricted voting rights to seven Prince-electors including the Prince-Archbishops of Mainz, Trier and Cologne alongside the King of Bohemia.
Most new kings were crowned at Charlemagne's throne in Aachen Cathedral after their election. Philip of Swabia was an exception who received his coronation at Mainz Cathedral in 1198 before another ceremony occurred in Aachen.
Henry IV adopted Romanorum Rex as a title to emphasize his sacred entitlement to be crowned Emperor by the Pope. He continued to regularly use the title until he finally was crowned Emperor by Antipope Clement III on the 2nd of May 1084.
The title Romanorum Rex ceased to be used for ruling kings after 1508 when the Pope permitted King Maximilian I to use Electus Romanorum Imperator. This change occurred after he failed in a good-faith attempt to journey to Rome.
Charles V was the last king to receive the Imperial Crown at the hands of Pope Clement VII in Bologna during 1530. The Holy Roman Empire dissolved in 1806 ending the constitutional law that governed these elections.