Hi AVR Geeks, I need some suggestion for my project for a robust design and implementation. My project is to develop an IP testing device. We need a keypad, LCD display, UART0 for debugging, UART1 for communicating with modem, Web Server, RTP stack, two peripheral sensors. I would like to ask which design should I follow? Can I use the FreeRTOS for all this tasks? Or should I approach with the normal way  like looping and using sleep and deviding time between all my task?

That is up to your application. Some applications benefit from an RTOS some are better without. Take a look at http://www.freertos.org/FAQWhat.html#WhyUseRTOS