In Lightroom, photos can be resized when you export. So, in the export dialog box, go to the Image Sizing section and enter the desired size in pixels. (Note: if this is a different aspect ration than the original, you will have to crop the photos to the desired aspect ratio before you export)
These are Mobile apps and do not have an export feature. They have a share features which do not allow for specific sizing.
Photoshop Fix can crop your image and will change the physical dimensions by the nature of a crop but there is no image size dialog for you to specify a dimension
Lightroom can also crop but will not allow a specific dimension either.
Images can be resized in the desktop version of Lightroom as @dj_paige points out.