✔ 最佳答案
"What are the differences between Quasi Sovereign bonds and Sovereign bonds with regard to safety in investment?"
The "quasi" part means that it is easier for the govt to default on the debt. The big example is Dubai World (which you can Google) which was quasi-sovereign debt that defaulted and the govt did not default on its sovereign debt. In the US, the big provider is FNMA/FHLMC and nobody exactly knows if teh govt could withdraw its guarantee on those bonds (it would be a huge disaster so they probably won't).
"In case the agency bankrupts, can the bond holders get back all their money from the government?" It depends on the quality of the guarantee. For instance US GNMA and German KFW paper is as creditworthy as govt debt. There is the full faith and credit behind the paper. At the other end is Dubai World, where people did not get paid.
"Is Lehman Brothers Bond Quasi Sovereign bond?" Is that a joke? Of course not.