I have a raspberry pi board which I will like to use as a general board(like motherboard). My aim is to be changing the software periodically(just like reinstalling a new windows is). Can someone guide me on how I can do this? Or do I need to write something like a bootloader to the board and also program an OS for the purpose? I have some experience in programming hardware(AVR) and also CWhy not https://www.raspberrypi.org/downloads/raspbian/ or https://archlinuxarm.org/platforms/armv6/raspberry-pi? I haven't played with a Pi since the first gen, but those are certainly robust and well-supported operating systems.

You might also want to check out https://www.reddit.com/r/raspberry_pi/, it's a very active community.Also, You Tube has lots of things about Raspberry PI with links to related sites.
https://www.youtube.com/raspberrypi
FRIEND of mine has a Raspberry PI with the MicroSD reader which is used for the OS and Software that is run on the PI. The PC is used to build the MicroSD Card for the PI and then the MicroSD Card is placed into the PI and PI booted and it runs what is on the MicroSD Card.

I haven't gotten into the Raspberry PI's because I feel its too limited for my needs. If I needed to automate machinery it could be used with its I/O to control a system based on a feedback loop and logic. For it doing more than I/O its not all that powerful for graphics rendering etc. Some have used them to make media players and kiosks with them and I SAW an arcade project but the video playback can be choppy at times because of its low power consumption ARM processor can only do so much.

If you want to learn how to accept an input and perform an OUTPUT to turn something on and off its perfect for that. But my friend has had issues with stuff beyond simple I/O and I feel its because its not that powerful CPU processing and GPU wise.

Maybe a newer MODEL than his is better as these are evolving and getting more powerful, but just stating from what I know about his device.