Pronunciation, context and most importantly most of these sentences wouldn’t be used like that. (Except for “die spinnen”, i say that probably daily)

Emphasis on different parts and context.

Context. In the first two examples both sentences sound exactly the same, but it has never been a problem.

In some examples I‘d maybe expect stronger emphasis on the noun. ‚Sucht‘ (short u) vs ‚sucht‘ (long u) from the last example are pronounced very differently.

Good question! Sometimes it’s stress but sometimes just context