What Islamic marriage practices are less used today than in the past?
arranged marriages, a dowry and polygamy (when a man or women has more than one spouse without getting divorced)
Most people of medieval Europe were Roman Catholic or Eastern Orthodox. Some were Jewish or Muslim, and some were pagan. Apart from the pagans, the religious practices of these groups were very much as they are today. I have long regarded any description of pagan practice as suspect, because I have never found any that were written by the pagans themselves. Christian religious practices included baptism, confirmation, marriage, confession, and unction for those who were…
Islamic Law, or Shariah must be applied in any Islamic state. Nowadays there is no Islamic state, just countries where the Constitution and the laws are more or less inspired from the Shariah. All the countries that have Muslim population as a majority have altered laws from the Shariah. People tend to think that all the laws of a country where there are Muslims are "Islamic", but they are wrong.