This is the default internal configuration :
few questions :
- Can I define port1 (WAN) as VLAN1 - so to have 5 ports lan and no WAN ?
(without deleting WAN interface in the cpu)
- Is it possible to use Port6( cpu eth0) as the inteface for both WAN and LAN vlans ?
(without using port0)
- If I play with configurations of the switch and make a mistake can I restore to factory default ?
You can move WAN to VLAN1 and see what happens, you will not break the LAN interface, and will be able to log in and reconfigure it.
If you do the change in Luci, after you hit the save and apply button, there will be a timer for rollback. If you break the network somehow and the PC cannot communicate with OpenWrt, the rollback will restore the previous working configuration.
I think that since you have ports connected on different ports of the CPU you cannot just assign them all in the same VLAN. What I would do is to delete the wan interface and add the eth1.2 physical interface in the lan interface along with eth0.1
You can leave VLAN 2 in place with only port 6 remaining attached to it. Of course a switch VLAN with only one active port can't actually pass any traffic, but it is a legal configuration.
It's a good idea to connect by wifi while doing this so even if you totally mess up the Ethernet ports you don't lose access to fix it.