Sony Ericsson :: Vivaz - Downloaded Application Compatibility

I was just wondering if anybody else knew about the following or if it is wrong and may harm my phone. I went onto the playnow site on my phone via internet search. Whilst on it I scrolled down the bottom of the screen and clicked free stuff and lots more stuff came up available than when I go on playnow on my laptop. I downloaded a few and they all seem to work although they pop up with a strange type of keypad thing under neath the application when its open.

I then went back onto the play now site. I was on and was looking about when I noticed it had a bit that said : country - uk your phone - w880i. I didn't put this in it was already there. Mine is the Vivaz handset and yet the applications seem to work ok under the w880i phone. Should it not be compatible? should I remove the apps I downloaded this way of my phone to prevent a problem etc? I am so confused at the moment as to whether it is safe etc. for my phone. As I didn't expect it to happen. I always thought when you go onto a site like play now it would know what phone is being used.