1. Let's assume I wanted to transfer some ICN coins/tokens either from my wallet on the iconomi site, or from my wallet on Kraken to myetheriumwallet ...
Obviously the myetheriumwallet was designed to hold etherium coins. So now i am going to send ICN tokens to an address in this wallet- which was actually designed to hold etherium...
So how does the wallet "know" after the transfer has been done (and hopefully succeded) that the coins/units held in that partticular wallet address is in fact ICN and not etherium?
The ethereum address was not designed to hold ethereum coins only. it was designed for smart contracts and app tokens also. Your address will hold ETH balance and any ECR 2.0 type tokens linked to the address also. ICN is a token so it will be stored by the same address. Its up to you how you organise your holdings. You can have ETH stored by a different address than the one storing ICN ... you can split your holdings so that if some keys are stolen you don't loose it all. But you can keep all ETH related things linked to the same address.
I just want to add one thing about myether, or any other blockchain-based wallet (including Bitcoin wallets):
You and the wallet don't hold the token. The "money" ,so to say, is not in your wallet, but on the blockchain.
The network has agreed (consensus) upon which address (public key) holds how much of that cryptocurrency. For the Bitcoin blockchain it is bitcoins,
for ether blockchain these are ethereum and/or any other app tokens.
When you want to spend the money, or part of it, you prove ownership to the network by signing with your private key, which is encrypted by the password you must provide to the wallet interface.