Let me assume you are talking about iStock? If not feel free to name the agency.

For iStock it's absolutely normal to approve your application based on images that they will not accept for their collection.

I know it sounds like it doesn't make any sense but that's how they are. Once you figure out what they accept it's a piece of cake.

As its 'another agency' I can only guess...
but I have had something similar, some agencies don't ask for your full resolution images to become a photographer - I assume those agencies are looking at the style and subject choice of the images you take not the technical qualities. As soon as you submit the full resolution it (presumably) would be easy to get rejected if they were not also technically good.

One doubt! I sent 3 of my best photos to one agency as my contributor application, who has been accepted! Next day i uploaded the same 3 images to my portfolio, and all have been rejected!

Is this possible? Are they kidding with the people? 

Yes and yes. It's microstock. They can make the rules and change them at any moment. They can accept an image and reject it two years later. They can sell something and give the money back. They can do anything and do just about that, including changing levels, commissions, best match, what's acceptable, or anything else.

Welcome to microstock.

In your case it could be as simple as the person who does accepting applications being smarter than the reviewer who later rejected your images. Or that review for admission isn't the same as review for going on sale. It's that simple.

Mea culpa!     
Some images were taken in a public place, but with graffitis included, so there are possible hazards, that some unkown graffiter sue me and the agency!

I will delete these images from other agencies, right now!
Starting to learn!