Constructive criticisms are welcomed(and very much needed).

I did this in GIMP - my biggest issue was matching the colour of the belly to Tessa's belly, and getting the shading and everything right. What's there is a combination of some recolouration, smudge and burn, and an eventual reaction of "that's the best I can manage".

Nonetheless, please do give me any tips you have, or just let me know if you'd like to see more.

First publish morph you mean. You have been working you backside off in practice. The only thing I can offer is do just a little more work on the nipple and surrounding area in texture.(roungh it up a little)
You are good junior. btw your choice of model,SHAZAM!

I think you have done a great job! And love to see more of your work

nice one

Here's another one, with the original for reference. This one was more about the boobs, but I figured there wasn't any harm in giving her more belly too.