An 'dinosaur' reply from how most of microstockers call us macro stock photogs:
First of all to apply to alamy you must have camera which is good enough for Alamy... You may find your camera in list there and then be sure that you have images on about as said... More than 48MB ;-)
Other thing what you are wrong is that your images are ALL rejected if one found as failing in QC. It is usual there.
Not more or less than 4 images are allowed in initial submission. All 4 images will be reviewed and if just one fails, your whole batch is history. Their reviewers do not comment any more than necessary. So, you will get one marked and your batch rejected. If you are lucky then you may get some more comments or marks... But, it is rare there.
If you receive fail on your initial submission I advise that you find other four images and try with them.
BTW, it would be very good for you to read all about submissions there because they work quite differently than many other sites you are used to.
For me, their system is very smart and very effective.