Yes, it is possible. If you have two Lightning Network nodes built on top of two networks, then you can swap the coins. So, if you use LN-BTC and LN-LTC, then you can swap between BTC and LTC.
Can it be used to serve the mission of an exchange? Like - Is it possible to create hundreds of lightning networks over a single platform? Can we only use it to do a swap or this also be used in future trading over DEX?
I did some research and found that COSMOS SDK and Atomic swap will also help somehow in DEX.
If the lightning network can bring all the features I mentioned can you explain a little that how by pointing some points, That should be great and easy to understandable for anyone who will be looking for this kind of information.