I don't know the name of the plant. It's a common house plant in Bangladesh. What interests me about its flower is the colorful leaflike structure that probably functions as a petal. What is this structure homologous to? Petal, sepal, bract or leaf?
The plant looks like something in the genus Bougainvillea. These plants are native to South America, but found as introduced ornamentals in many places.
The colored petal-like organs are bracts (see the Wikipedia link above). The entire structure is an inflorescence with the flower buds growing out from the surface of the colored bracts — you should eventually see those flowers open and you could then dissect them confirm that the usual flower structures are present.