How does it determine where are the stresses? Is it based on just the word itself?

I'm very new to English poetry, I might be entirely wrong here. But when I input some famous poems, the way this app puts stresses is quite a bit different from my understanding.

For instance, for

> Bards of Passion and of Mirth,

It sees _and_ as unstressed, the second _of_ as stressed, and _Mirth_ as unstressed, which doesn't quite make sense to me to be honest.

> Tomorrow and tomorrow and tomorrow

It sees both _and_ as unstressed, while my understanding is that this verse is better read as fully iambic, putting stresses on both _and_.

> And what is love? It is a doll dress'd up / For idleness to cosset, nurse and dandle

https://i.imgur.com/raPMDnc.png

It sees four consecutive unstressed syllables. I'm not sure what is the logic here.