Dandelion is the commom name used to make reference mainly to Taraxacum officinale, but actually is also used to virtually any species of the genus Taraxacum. I mean, a lot of species are known as Dandelion, hence this name comprises a lot of morphologies.
Also, there is something called "Phenotypic plasticity", which refers to changes in the organism characteristics due to adaptation to environmental factors. (I.e. one species may have different morphologic and physiologic traits in response to environmental variation).
Regarding to the photos you posted, it's not safe to tell you if these are the same species or not, because one would need way more detailed images, mainly from flowers, to give you a more accurate identification.
There is a Fabebook group named DetWeb, where botanists identify plants if you post good enought photos... It's a brazilian group, but you can post in english, of course.