In poetry,which syllables and words get stressed ?

Isn’t that to the reader?

In theory, you are supposed to pronounce the words naturally. The rhythmic form is a constraint on the writer, not a task for the reader. In practice, however, many poets have taken advantage of their audience’s familiarity with a particular form to fit a word or two into a place where pure theory would say it doesn’t belong. In many cases, this works out fine. But if you do it too much, the form loses its meaning and you might as well just be writing free verse.

Pretty sure the focus is on the last syllable.

Definitely the rhyming ones, under constant pressure to impress…I got this wrong didn’t I?

There are many different traditional forms and conventions and styles for poetry. And infinitely more non-traditional ones.

In simple common English poetry, it’s often the last syllable of each line, which also rhymes.

In iambic pentameter, you have lines of five pairs of syllables, with the second of each pair stressed, and a pause between each line.

Or in heroic meter (e.g. Homer or Virgil) it’s similar to iambic pentameter but was actually dactylic hexameter, e.g.
armA virUMque CAno TROIae PRIma AB orIS.

or…

or…

I think it totally depends. You can always watch some well done Shakespeare plays to get a feel for it.