Considering that all Supreme Court appointments must be confirmed by Congress, it seems unlikely that an unqualified person would wind up being both appointed and confirmed. However, if that were to happen, this unqualified person would probably issue no formal opinions and let the more qualified justices do all the talking. He could then vote on a purely ideological basis, whether liberal or conservative, whatever his particular political leaning may be.
president of India
vote for approval
the president in consultation with chief justice of the supreme court
the president appoints them and the congress questions them
it is the house of representatives
If the president of the United States dies in office, a judge will normally swear her or him in. This has happened on several occasions.
President Obama
Taft
NO
vice president
The president's power to nominate federal judges is a check on the judicial branch by the executive branch.
The Executive branch gets to choose candidates for federal judgeships, including Supreme Court Justices. The President also has the power to pardon people convicted of federal offenses, Since the President controls the Department of Justice, he has some leeway in how laws are enforced.