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The primary or secondary is only a matter of viewpoint. Apply AC to the 10 turn ratio side and you'll get 1/10th out the other, apply ac to the 1 turn ratio side you'll get 10 times out the other, the primary is which side is driven by power. Obviously with wire thickness to consider there are power consideration in what you can safely step up and down.
No load voltage is one way of measuring it, but commonly with a transformer the 'voltage' it's rated at is at a it's rated current. No load voltage will always be higher.
Yes that can be a little confusing. The voltage ratio and current ratio work in reverse, so if you step up the voltage by 10 you decrease the current by ten, and if you step down the voltage by 10 you increase the current by ten. For learning purposes just assume the transformer is a 'perfect' device so power into the primary will equal power out the secondary. In real life there are some losses as nothing is 100% efficient.