The IP address includes the device you type at, any router (wireless WiFim cellular), the modem, and your ISP. So you can see that 3/4 of it pinpoints your house.
This makes it relatively easy to see how many devices (phone.tablet, PC, etc) are accessing anything from your house.
Your account has at least that IP address include in it's historic record. But it might (probably does) also include all the IP addresses that your device has ever accessed the site from (internet cafe's, cell towers, w/e). But your account does not = the IP address.
Your account can only be logged in from anywhere once per session. Sessions starts with a login, and ends with a logout. So changing devices is good if you shut down the
App (effectively logging out) before logging in on the other device.
With modern programming there should be no reason that you couldn't start a game on one device, play some, log out, then go on the move while playing on a mobile device. Or vica versa.
What you CAN NOT do is be logged on to an account more than once at a time.
There is currently a caveat to this tho. You can be logged in to both your ACR, BCP, and maybe even True poker accounts on different devices at the same time. These are all skins on the WPN network, and something they (WPN) probably want to fix.
The CC Leaderboard will catch these double dipping incidents, and will cause you some grief. Like a suspension from the PW thread for 30 days, and a black blob on your record. (A black blob is the opposite of a Gold Star). Also, the LB will deny you credit for the points during that game.