Add the seedless pulp to the blender and the water and puree for a minute or two.
In a large enough bowl, beat the heavy cream with a hand mixer for about 10 minutes until the cream is stiff.
In another mixing bowl, add the condensed milk and carefully fold in the whipped cream.
Add the soursop pulp, lime juice, vanilla extract, cinnamon powder, salt, and incorporate well. Careful not to over mix.
Pour the mixture into a freezer-safe container, cover and leave to freeze for at least 8 hours.
Notes
Note that the instruction assumes you have already peeled and removed the soursop seeds and core.
I pureed the soursop pulp with little water and didn't strain, which means there will be soursop bits in the ice cream. If you want smooth ice cream, you can either blend the pulp instead of pulsing or add more water, pulse and strain and use the juice to make the ice cream.