Is it possible, to turn A Raspberry Pi into a router and share USB port into network and access on network of Pi?
Yes this is possible as the USB port on your Pi is able to handle more than a single device if you use a hub. This is demonstrated on the Pi b which utilizes the same processor but also includes a USB hub built onto the pcb which allows for the second USB port and Ethernet to exist. It is possible to share the pis USB port over a network as well, I'd recommend you look into samba as shown here I'd also recommend against using the Pi as a router as it's slow
You can build your Pi into a NAS server as well by using Samba (Like above). If you want to connect the external HDD, you need to mount it
sudo apt-get install ntfs-3g
and then install the Samba services
sudo apt-get install samba samba-common-bin
You can do it step by step through this post with full images : click here
This is (largely) automated with OpenWRT, by adding some packages and configuring them via LUCI webinterface. I did something like that long ago. You can search for and install the packages from LUCI - it is almost as sleek as WebGUI. I set up some DLNA stuff IIRC, without using ssh to login once. Samba is in their repository, as are some afp/nfs packages that work almost automagically.
I have not looked at OpenWRT, but it is worth looking into for the Pi3 alone, since it costs less than a 'new' router, and likely has better support for e.g. RTL8187. Whether that works in HostAP mode is not something I've looked at, but if the onboard wifi of Pi3 is not yet supported, it will be SOON.