RE: the Divine Liturgies of East or West being unchanged since the apostolic age
In general, the ancient structural core of the Divine Liturgies of both East and West is identical with the Eucharist of the apostolic age. Several important factors must be taken into consideration concerning liturgical development.
Liturgical language and popular language: When the language of the Liturgy is popular there is a centrifugal tendency to move liturgy to reflect current concerns. This centrifugal process of liturgical change may be sudden or gradual but always at work. In general, Western liturgy ceased being in the popular tongue about the 6th century (and has only recently returned). A special liturgical language for the West then replaced the popular tongue in worship bringing to a halt this sort of liturgical development. In the East special liturgical languages developed later, after the 15th century, in general. Therefore the period of liturgical development of this kind was more protracted in the East than in the West.
Nature of liturgical worship: Divine worship develops and grows in a special way in monastic communities, state courts and Patriarchal sees. Monks have a tendency to mold worship to fit their own circumstances. This process of change may be seen in the variation of worship among the various monastic communities. During the Middle Ages in the West and afterwards in the East monastic communities exerted a profound influence on the shape of divine worship. The variation of monastic worship after 1453 is one of the challenges that those who have sought to codify Eastern worship into a single tome have experienced. State courts profoundly effect worship. Byzantine, Frankish and Anglican Imperial courts have all impressed their own stamp on worship. Finally, Patriarchal sees each have an effect, over time, on liturgical worship. Patriarchs have impressed the episcopal worship of their sees on those in other localities. Historically, worship has had 2 major poles. Christians have experienced the various developements of Latinization or Hellenization. In the West, Rome has engaged in 3 major reforms of worship: Gregorian, Tridentine and Paulan (Vatican 2). In the East there have been local attempts to either codify or reform worship, but none have addressed the various major imprints that Imperial, monastic and Patriarchal have left on Eastern worship. The delicate balance that must be struck by those that celebrate a living liturgy faces both East and West, today.
Not sure what source you are using -- NT Greek ceased to be the language of the Liturgy for the West at the end of the 2nd century, and became Latin. Latin was the "popular" language, since it was spoken by Latins (geez!), but the liturgical Latin was way above your average Roman, as any liturgical language is not the same as "vernacular," i.e. spoken language.
After that as far as I know -- until the Vatical II - (liturgical) Latin remained the language of the Latin Church universally for all liturgical and ecclesiological rituals.