lsmod shows that vboxguest is loaded, but not vboxsf - perhaps it loads when needed.
If you add the script to your extension you need to give it the same name as your extension i.e. vbox7.
Sorry I just realized after I rebooted few times and do lsmod with different scenarios gave exactly same result:
1. boot TinycorePure64 then lsmod
2. boot TinycorePure64 then tce-load -i vbox7.tcz then lsmod
3. boot TinycorePure64 with vbox7.tcz in onboot.lst
All these 3 methods actually gave output the same like the one i posted above (before this reply).
I guess sudo ./VBoxLinuxAdditions.run probably not compatible with TinycorePure64.