SDF and SPEF usage with PT

Do we need both SDF file and SPEF file for static timing analysis using Prime Time ? or is that enough if we read either one of them for static timing analysis using PT ?

Can backend tools (like IC compiler) write out both SDF and SPEF ?

For different PVT corners SDF file will be different. In the similar way, will the SPEF file also be different for different PVT corners ?

Do we need both SDF file and SPEF file for static timing analysis using Prime Time ? or is that enough if we read either one of them for static timing analysis using PT ?

either SDF or SPEF+.lib is enough

Can backend tools (like IC compiler) write out both SDF and SPEF ?

Yes

For different PVT corners SDF file will be different. In the similar way, will the SPEF file also be different for different PVT corners ?

Yes

While doing STA, SPEF is usually preferred as it contains info about the parasitics too which the SDF does not have.

SDF is generated by primetime while SPEF is generated by STAR RC. IC Compiler is used for placement, routing and clock tree synthesis.It cannot generate either a SDF or a SPEF.

Both SDF and SPEF will be different for different PVT corners.

SDF is a delay format , it could be written out of DC, IC compiler and PT all 3. The source of the delay differs .. From DC / ICC it could be Wire load models or TLU+ files. This SDF can be used for forward annotation / back annotation.
However, it is preferred to use SPEF in PT because we also reort for Design rule constraints like max trans and max cap which cannot be computed from SDF because it does not have information about the transition and capacitances. It only has a composite delay value for each cell and cell to cell.
Just like SDF SPEF is also different for different corners. That is how it is written out.
Ex : For a corner Pfast_V090_T110 - the SPEF is written out of STAR_RC then fed to PT and then write_sdf gives the sdf for that corner.