Yes plants do adapt to were they live. Some plants go dormant when there is a shortage of water. Dormant means that it sleeps and does not take in anything. Some seeds actually do that because in the desert there is not that much water. So when the rains come it wakes up and grows.
Yes, plants will die if they do not store water or go dormant. They need these adaptions to live in the desert.
Yes, plants do need sun. Some plants have some adaptions to help with that to. They die without water, sun light , and adaptions to live in some places.
Nicolette