Final answer:
The fungus described in the question is most likely Candida albicans, known for causing conditions such as candidiasis and thrush.
Step-by-step explanation:
The characteristics described in your question, such as the production of terminal round chlamydospores, clusters of blastoconidia, germ tube formation within 3 hours, and assimilation without fermentation of sucrose, are consistent with a species within the genus Candida. Specifically, these characteristics align with Candida albicans, a type of yeast that is commonly studied due to its role in human health and disease, including candidiasis and thrush.