Is it true that letting babies cry in the morning can make their heart and lungs grow stronger and letting them at night can make them gassy?

It shouldn't be the case as crying won't strengthen their lungs, nor would crying at night make them gassy. Babies cry because they want something or there's something that they can't communicate. Crying is actually pretty hard on a baby, so it's best if you try and console your baby as soon as they cry. :)