1, not needed.
2. There are all the major financial websites, but the information provided is quite complicated, and many individuals can't participate. The following websites only provide the most timely information for individuals. For newly issued bonds that individuals can participate in, the table on the securities page is very intuitive.
3, as long as the national debt can only be sold by specific institutions. Corporate bonds, like stocks, can be purchased with securities accounts and traded in the chronological order of declaration, unlike the new shares of stocks that need to be drawn by lottery. But now there are very few individual issues, so it is difficult for individuals to grab them, and they can only buy them in the secondary market.
The process is nothing special, just like buying and selling stocks. Bonds are operated by T+0, with low handling fee and no stamp duty. But the yield to maturity of bonds is the most important thing. Unlike stocks, everyone has different opinions on its valuation.