NOC issues for cancellation of agreement from builder

Hi all, So my issue is that my mother has given title to build apartment to a builder (say ABC) through an agreement, Further the key fact of the agreement with respect to the time of completion of project is stated as, "4 YEARS FROM PASSING OF ARCHITECTURAL MAP. so my 1st question here raises as, is the agreement correct with respect to the time seems not clear. if like the builder passes his so called MAP IN 4th year (after the date of agreement), and the completion date start from that date. then builder would take another 3, or 4 years to complete the projects and the owner would wait now 7 years to get the possession as per agreement. is it worthy/ justice as per said agreement. Now the 2nd issue with respect to the above issue is, after completion of 4 years form the date of agreement, the owner requested to cancel the agreement for non performance of builder to build apartment. The builder here gives only a date for returning back the property cancellation of the agreement and denies. So after 5 months before cancellation of the first agreement, the owner of the property made agreement with another( say XYZ ) builder in good faith thinking that the 1st builder would cancel the agreement. Now the 2nd builder had possessed the property under his control and now the 1st builder (ABC) black mails to cancel the property by giving him 5 lac ruppees to cancel the agreement and threatens to file a suite file so that the apartment would not be built by the 2nd builder saying the owner that you had made agreement with another builder without cancelling the 1st agreement with me. here what should the owner of the property do to come out with this situation. is there any remedy to the owner from the 1st builder.