Which of the followong opreations on the Fischer formula does not change its absolute configuration ?

Which of the following does not change its shape?

Which of the following representation of the Fischer projection formula is the meso isomer of 2, 3 dichlorobutane

Which of the following combinations amongst the four Fischer projections pepresents the same absolute configurations?

Which of the following combinations amongst the four Fischer projections represents the same absolute configurations ?

Which of the following lanthanoids does not contain 5d electron in its valence shell configuration?

Which of the following statements regarding the Fischer projection formulae given here is right

Which of the following ions does not have the configuration of argon ?