I want to use Magento Community version to build my site for commercial purpose but before that I am having certain queries below:
Thanks in advance.
1. You can build a website powered with Magento OS and sell stuff. That is possible and many others do that. Although you cannot take Magento OS source code and resell it.
2. I don't think so. That doesn't make sense.
3. It all depends on your hardware and the way you setup and optimize your Magento store. I have seen people successfully processing 10k orders a day with Magento Community Edition. Although if you are planning to handle over 1M of SKUs you might get into performance problems.