1. Pay attention to check whether there are any changes in important terms in the contract, such as area, price and delivery date. If it is not modified, you can ask for a new signature, which has no direct harm to your interests and may indicate that some public data have been modified;

2. If you find that the developer changes the contract without authorization and infringes on your legitimate interests, you should immediately report the complaint and keep the evidence to claim compensation from the developer. This situation may be that the developer violated the rules in the area declaration, failed to reach the original agreement, and did not want to publicly apologize and refund. Therefore, it is intolerable to secretly modify the contract, and the developer must be responsible.