Malhar, so is your Pakistan Larkana tree large enough to start holding fruit yet? Did you taste it on your tree?
I got cutitngs of the Taiwanese Long, Indonesian Seedless, and two other varieties from this person. He mentioned the same about 2 of these large white flesh guava fruits. He said the fruit starts out hard (size is medium-large) but if you wait until the outside of the fruit starts to turn a little yellow, then it gets a little softer and is sweet (for a guava).
I found another guava fruit on the ground there, it was not the hard crunchy type, it was more like the Sylvia guava, the fruit gets pretty soft when ripe. I noticed this fruit which is about the same size as the Mexican Cream (2-3" long) because the inside flesh was pink/red. After I asked about it, he said it was called Ruby Supreme. He got it from a nursery.