Hey manoj welcome to wpcentral forums :smile:
Though in the sdk , developers were able to download and upload files but I can not say where it saves , just one more day and you will get your complete answer
File manage is expected , it would same as one found in windows 8.1 skydrive app. I haven't seen windows phone 8.1 as it is not yet official showed to users , it will be shown in media tomorrow
They used a trick to be able to download and install it, but it still doesn't function. Basically it is just so they can brag about something that is in reality not usable.