Revision of Development plan.

At least once in 1[twenty years] from the date on which a Development plan has come into operation, and where a Development plan is sanctioned in parts, then at least once in 2[twenty years] from the date on which the last part has come into operation, a Planning Authority may 3[and shall at any time when so directed by the State Government], revise the Development plan 4[(either wholly, or the parts separately)] after carrying out, if necessary, fresh survey and preparing an existing-land-use map of the area within its jurisdiction, and the provisions of sections 5* * * 22, 23, 24, 25, 26, 27, 28, 6* * 30 and 31 shall, so far as they can be made applicable, apply in respect of such revision of the Development plan.