The correct options are
B Shortest distance of the chord from the centre is the perpendicular from the centre.
C Perpendicular from the centre of a circle bisects the chord.
Option A is wrong as the longest chord in a circle is the diameter which is 2 times the radius.
Option B is correct because the shortest distance between any point and a line is the perpendicular distance of the line from the point.
Option C is correct. Perpendicular from the centre of a circle bisects the chord(Theorem).
Option D is wrong as angle subtended at the center by a chord is twice the angle subtended at the major segment.