The supreme court serves what important function in the us federal government

They made a checks and balance system to equal power within the branches. the "check" meant that one branch would watch one branch and "balance" them if they were too powerful. if you want more info on this, i would just google checks and balance system.

The president of the united states does not have the authority to “limit” the power of the judicial branch. however, the president can influence the political direction of decisions made by justices on the supreme court through the nomination process when a position becomes available.i would say the best answer is that he can at least interpret the laws