cry out / crying

  1. I heard him cry out in pain.
    1a. I heard him crying out in pain.
  2. I heard her cry out for hours.
    2a. I heard her crying for hours.
    Are these sentence correct?

1 a and b, yes

2 - correct but it is unlikely that under most circumstances ‘out’ would be used there.

cry out = calling / shouting out

2a correct