Star formation in extreme environments such as HII regions is always challenging and can be significantly different from that in quiet environments. HII regions are generally associated with OB stars, which usually form in clustered mode and have profound effect on the parental molecular cloud. The observations of star forming regions can be used to address several questions regarding star formation such as; what are the observational properties of different phases of star formation? How star formation proceeds within a molecular cloud? Whether the star formation is a coeval process? If not then which star forms first? Whether with the formation of massive star(s) in the region, star formation ceases or alternatively trigger(s) new generation of stars through various processes. Therefore, HII regions containing massive fragments or protostars are ideal targets to study different phases of star formation. Which mechanism (spontaneous or triggered) is dominant in a region, is necessary and vital to understand the star formation process within a complex. In this thesis we have tried to answer a few of the such interesting questions. With the advent of new data from deep optical, near-infrared, mid-infrared and X-ray surveys, a considerable interest has been evolved to study low mass young stellar objects (YSOs) as well as to study the evolution of circumstellar disks around the YSOs associated with young star clusters. Several X-ray studies of low-mass PMS stars have been carried out which revealed very strong X-ray activity. The influence of a circumstellar disk, and particularly the influence of accretion on X-ray activity has been of special interest. X-ray studies of PMS stars in star-forming regions have yielded contradictory results. Hence we have re-analyze the X-ray properties of Class II and Class III sources and the relation between rotation and X-ray activity in TTSs using the sample of the YSOs identified by Pandey et al. (2013) and the rotation period of the YSOs determined by Lata et al. (2012), Lata et al. (2014) for the YSOs in the field of young open cluster NGC 1893.