Least Count of the Scale Used
The least count of a measuring instrument is the smallest value that can be measured accurately using that instrument. In the case of a scale, the least count refers to the smallest division on the scale that can be measured.

In this case, the least count of the scale used is given as 1 mm. This means that the scale can measure values in increments of 1 mm.

Name of the Distant Object
The question does not provide the name of the distant object. To answer this question, you would need to provide the specific name of the object you are referring to.

Distance between Concave Mirror and the Screen (f) in cm and m
The distance between the concave mirror and the screen is denoted by the symbol 'f'. It is the focal length of the mirror, which is the distance between the mirror's center of curvature and the mirror itself.

The question asks for the value of 'f' in both centimeters and meters. The specific value of 'f' is not provided, so it would need to be given in order to answer this question accurately.

Mean Focal Length of the Concave Mirror (f) in m
The mean focal length of a concave mirror refers to the average value of the focal lengths of multiple concave mirrors. It is denoted by the symbol 'f' and is measured in meters.

To determine the mean focal length of a concave mirror, you would need to measure the focal lengths of multiple concave mirrors and calculate the average. The specific values of the focal lengths of the concave mirrors used are not provided in the question, so it is not possible to determine the mean focal length without additional information.

In conclusion, the question provides information about the least count of the scale used, but does not provide the name of the distant object, the distance between the concave mirror and the screen (f) in cm and m, or the mean focal length of the concave mirror (f) in m.