If I use VPN for my other PC in my same network but the IP id different. still can use the Unlimited SubscriptionI or the IP must be same ?

Hello,

No, with VPN on one computer and not one the other, the unlimited subscription is useless (your public IP change, you cannot launch more than one WRobot session at the same time). You can use the same VPN server (same ip) on the two computers if you want run more than one WRobot session.

If you want use one IP by wow account, you need to buy normal subscription (one by Wow account). I have added discount if you buy several normal subscriptions (send me private message if you want custom price).