Muslims say that Islam _was_ the religion of all the prophets you've mentioned. Because of this they also believe that Islam is the _oldest_ religion, since Adam, the first man, followed Islam.

Practices in Orthodox services can differ. For example, in some Romanian parishes everyone has knelt while the Gospel was being read, but I have never seen this elsewhere. And as the other poster mentions, full prostrations are done (and widely across the Orthodox world) in certain contexts.

Some churches in Greece and Albania have pews -- the concept was brought back from the North American diaspora where Orthodox parishes were set up in former Protestant or Catholic church buildings -- so you can do all the standing, sitting, and kneeling you might be accustomed too.

Churches probably have some kind of theological explanation, but alternately kneeling, sitting, and standing is much better physiologically. Having a large and diverse group of people all stay in the same position for an extended period is very rough on their bodies, and some more than others. Periodically switching prevents injuries caused by maintaining too much static load for too long in any one place. Probably also helps keep everyone awake. For the same reasons it's a good idea to occasionally switch positions while working.

there is something about prostrations that’s interesting but i can’t tell what exactly scientifically. But it brings me relief everytime I do it in namaz. I understand that the act of submission is relieving (things will be ok/there is someone looking out for me) but also physically (hard to explain)

no wonder it’s the meat of the entire prayer. Taking a prayer break from my messy code problems really resets my brain strain very quickly.

They're part of the Western (Catholic) tradition as well, but less frequently encountered: during the Litany of the Saints that precedes ordination to the priesthood those to be ordained are prostrate; the ministers at the start of the Good Friday liturgy lie prostrate before the altar; and a few other special contexts.