First of all set the jello not according to the packet instructions, instead use only boiling water about 1 1/2 cups for each flavour.
Set them until firm either outside or in the refrigerator according to the weather conditions at your place. I kept mine on the kitchen counter.
After setting, cut them into small cubes.
Now in a pan, mix the rest of the ingredients and heat on a low flame for about 4 minutes.
Add agar agar powder or strands into an another pan with little water and heat it on medium flame until it dissolves fully.
Add this hot agar agar mix into the milk and mix well. Switch off the flame.
Let it aside to cool down.
In a large rectangular glass dish, arrange the jello cubes first and then pour the cooled milk mix on it. Stir it well and keep it refrigerated for about 4 to 5 hours.
After 5 hours, slice them and enjoy. It should be consumed within 48 hours as it contains the milk substitutes and must be kept refrigerated.