Lightly coat three 8-inch (20 cm) square pans and one 9 × 13-inch (23 × 33 cm) baking pan with cooking spray.
In three separate bowls, mix each package of flavored gelatin with 2 cups (475 ml) boiling water. Pour each into its own greased square pan. Refrigerate for 1 hour.
After the jellos have been in the fridge for 30 minutes, make the milk gelatin. In a 3-quart (3 liter) saucepan, mix the unflavored gelatin into 1 cup (240ml) water. Set aside for about 5 minutes so the gelatin can bloom. Set the saucepan over medium-low heat and stir occasionally until the gelatin has dissolved. Add the whole milk and heat to just under a simmer. Add the cinnamon stick, remove from the heat, and let the mixture steep for 30 minutes.
Remove the cinnamon stick and whisk in the condensed milk, half-and- half, and vanilla extract. Set aside while you prep the colored gelatins. Remove the colored gelatins from the refrigerator and cut each flavor into 1-inch (36 mm) cubes. Evenly spread out and mix each flavor in the 9x 13-inch pan. Pour the milk jello over the cubes. Refrigerate until set and firm. 3 to 4 hours.
When you're ready to serve, invert the gelatina onto a cutting board, cut into 3- to 4-inch (7.5 to 10 cm) cubes, and place on a serving platter.