52. At any time after any improvement scheme or re-housing scheme has been sanctioned by the Government and before it has been carried into execution, the Kartripakkha may alter it: Provided as follows:- (a) if any alteration is estimated to increase the estimated net cost of executing a scheme by more than five per cent of such cost, such alteration shall not be made without the previous sanction of the Government; (b) if any alteration involves the acquisition, otherwise than by agreement, of any land the acquisition of which has not been sanctioned by the Government, the procedure prescribed in the foregoing sections of this Chapter shall, so far as applicable, be followed, as if the alteration were a separate scheme; (c) if owing to the changes made, in the course of a scheme, any land not previously liable under the scheme to the payment of a betterment fee, becomes liable to such payment, the provisions of sections 45, 48 and 49 shall, so far as they are applicable, be followed in any such case.