No, leftover chicken should not be reheated before freezing. It should be cooled quickly and frozen as soon as possible to prevent bacterial growth.
The primary goal when freezing leftover chicken is to minimize the time it spends in the 'danger zone' – temperatures between 40°F (4°C) and 140°F (60°C) where bacteria multiply rapidly. Reheating the chicken before freezing would only prolong the time it spends in this danger zone, increasing the risk of bacterial contamination. Instead, cool the chicken as quickly as possible after cooking. Divide it into smaller portions to speed up the cooling process. Once the chicken is cool to the touch, package it in airtight containers or freezer bags, removing as much air as possible to prevent freezer burn. Label each container with the date and contents before placing it in the freezer. When you're ready to eat the chicken, thaw it in the refrigerator, microwave, or cold water, and then reheat it thoroughly to an internal temperature of 165°F (74°C) before consuming.
To cool chicken quickly, spread it out in a shallow container or on a baking sheet. This increases the surface area exposed to the air, allowing it to cool down much faster than if it were left in a deep pot or container.