Hello @raj7, welcome to the Asana Community Forum!
You can add a task to various projects: Connecting Your Work Across Asana | Product Guide • Asana Product Guide
This way you can also move the task to add it to a project and remove it from another
Any task assigned to you will show under “My Tasks”
Here is a nice explanation as well: Move task from "My Task" to a different project - #2 by Charlie_Pilch