Multiple Accounts

Ya, it is very odd. Never seen this before. Generally only if you use two accounts at the same time.

It is what I have done. I am not going to bother getting my account reset, I have never even seen a "one account per platform" restriction before. Basically if you have to request a reset → new email for new account.

Unless it has something to do with merging accounts I cannot fathom the rational. Anyway I would not worry for your existing accounts. If you want to do allstars you might need to use a different platform.

I am sure there is a real reason and it is some way of cheating in the past but it does seem really odd without context.

(or are VIP consider illegal for the game).

Well @T0rr1e using a VPN isn't illegal as you aren't breaking any law, but using a VPN is against the T&Cs of the game.

5.5 You agree that you will not:

disguise, anonymise or hide your IP address or the source of any Content that you may upload; 

I wonder if King could find out?

Yes they can identify if you are using a VPN, but they can't determine anything else about you.

Think of the TOS as a catchall. They are covering everything possible regardless if it makes sense in the context of normal play. It just allows them to deal with situations of exploits where the wording for an exploit might not catch a very similar one that don't quite meet the traditional level of hacking and such.

Basically make almost everything against the rules to cover your butt but don't enforce it unless it is needed.

Multiple users connected to the same router doesn't mean they are the same person. Your whole family members could have just one account each. So, IP address cannot prove that you have multiple accounts.

If all your family members/friends login using one particular account （same location or otherwise） and play at the same time, that may be breaking the rule of "share your King Account or login information with anyone".

1. Starting a new game, without doing the dance with King, would require one. The other is basically inactive but it is technically multiple accounts. This is very common for games.
2. Say you are playing 1-500 to compare features across devices and even on the same device. It is much easier to make a new account than bother scrolling back.
3. Depending on device a new player gets a default setup. This was normal on windows. Also you would lose any progress if you did not want to bang out 500 levels or so in a row and keep using it to check here and there.
4. Going back does have one issue, you do not get streak and other effects. It is fine if you want to look at one board but not as good if you want to really test out playability.
5. Near the end of the game and want to go from the start but play differently while not losing that game and you don't have multiple devices.
6. Minor and likely fixed, but on the windows version your account would bleed over into any non account games. It actually could break the low levels. It was a "hoot".

It is exceptionally common to have a main account and an alt account for games. One is for playing seriously on, one if for mucking around.

Finally, disagreeing with my view of the world… you must work for King!!! :P