Someone else has already answered from a mechanical changes perspective so I won't repeat those.
From a trims and options perspective, it's rather futile exercise to track it all down, because there have been additions / subtractions / changes every year in terms of the option packaging, not to mention it's highly country-specific.
I'd say the biggest non-mechanical change is the infotainment system being overhauled twice (first in MY2018 with new incompatible h/w & firmware; then again in MY2020 with a new touchscreen system).
Honestly though, this is the type of question that deserves its own thread instead of threadjacking another one.
I didn't want to start a new one in case I missed a previous thread. Also, from the previous posts it didn't sound like many people were discussing things they didn't know about the Giulia