FAQ in Low Power

1. What are retention flops, where they are used?
2. what are isolation cells? where they are placed and why isolation's cells are used?
3. what is level shifter? what is use of level shifters?, where you will place them?
4. what is clock gating ?
5. what is power gating ?
6. what is MTCMOS switch, how will you place them?
7. what is UPF/CPF file, what kind of information it contain?
8. Difference between always ON and switchable domain?