It should be obvious enough, but perhaps you missed: you can install a browser, such as an old version of opera, by fetching its installer over the internet via ReactOS builtin "program downloader" (I do not remeber its name).
If you meant lack of default browser preinstalled though, I agree with you its lacking.
It's necessary to change the network card in VirtualBox for internet connection to work IIRC.
If you install 7Zip, you should know that 7Zip does not associate itself with file extensions by default. This is 7zip behavior. You need to run 7zip, go to options, and set associations by clicking on the '+' button.
If you meant lack of default browser preinstalled though, I agree with you its lacking.
It's necessary to change the network card in VirtualBox for internet connection to work IIRC.