When was the first parliament established?

Answer 1

The first English Parliament was summoned by Simon de Monfort, who was in rebellion against King Henry 111d, in 1265.
In 1215, a General Council was held with King John and this became known afterwards as a parlementum. This meeting gave us The Magna Carta.
Prior to that, other assemblies of the same general sort were called the Curia Regis, and the earlier Anglo Saxon Witenegemot.
The earliest recorded Witengemot seems to be dated 755AD.
Witengemots evolved from meetings the various Germanic tribes held which were named folkmoots. These probably predate written history in Northern Europe.

So, as the other respondent said, it's a toss-up.

Answer 2

Chris G has an excellent answer. Most teachers are looking for the Simon de Montfort answer in 1264-65 CE when he had captured the king (Henry III) and the nobles were briefly in control of England. Simon was killed in battle within a year,
but the tradition of parliament in England was established.

Answer 3

That's a tossup. The Faroe Islands' Logting dates from sometimes shortly after 825 AD. The Alting in Iceland began in 930 AD. The Manx Islands' Tynwald about 979 AD.