You have the possibility to access the central online storage worldwide via internet browser using the "Webdisk".
To log in, use your account id and password.
There are no practical file size restrictions for direct file access. However, if you access the NAS via the webdisk, the maximum upload size is 2 GBytes. The download is not limited, but should be completed in a reasonable time, e.g. to avoid problems caused by the forced disconnection every 24 hours, which is common with DSL connections.
In addition to a mobile version of the WebDisk web page, apps for mobile devices are also available for Android and iOS (keyword: HTTP Commander in Google Play or iTunes).