Follow the steps in order for the best result.
To prepare the crust: In a medium bowl, thoroughly combine the finely crushed graham cracker crumbs, 1/4 cup granulated sugar, and melted margarine. Press this mixture firmly and evenly into the bottom of a 9-inch springform pan to form the base. Set aside.
For the filling preparation: In a small saucepan, combine the cold water and the unflavored gelatin. Stir continuously over low heat until the gelatin is completely dissolved and the mixture appears clear, ensuring no granules remain. Remove from heat and let cool slightly.
In a large mixing bowl, using an electric mixer on medium speed, beat the softened cream cheese and 1/2 cup granulated sugar until the mixture is smooth, creamy, and free of lumps.
Gradually stream the slightly cooled, dissolved gelatin mixture into the cream cheese mixture while continuing to beat on medium speed. Follow by slowly incorporating the cold milk and fresh lemon juice until all ingredients are thoroughly blended and smooth.
Transfer the cream cheese mixture to the refrigerator and chill until it has slightly thickened, reaching a consistency similar to unset pudding (this typically takes about 30-60 minutes).
Once slightly thickened, gently fold the pre-whipped heavy cream into the cheesecake mixture until just combined. Be careful not to overmix, as this can deflate the whipped cream.
Carefully pour the creamy cheesecake filling over the prepared graham cracker crust in the springform pan, spreading it evenly with a spatula.
Place the cheesecake, uncovered, into the refrigerator to set. Allow it to chill for a minimum of 6-8 hours, or preferably overnight, until completely firm. For optimal flavor development and texture, an extended chill of 24 hours is highly recommended.
Just before serving, carefully remove the cheesecake from the springform pan. Adorn your delightful no-bake cheesecake with your preferred topping, whether it's fresh seasonal fruit or a luscious canned pie filling.