Not quite sure what you mean. Do you mean that all the learning data is stored in a blockchain? I think that would be a very ineffective way of handling so large amounts of data that needs to be accessed and written so frequently. A blockchain is just not suitable for this, but it would be possible yes, anything is possible.
Bullsh*t, there are no real AIs that could connect to the internet and interact with the world without first instructing it with codes and commands.
Smart contract can also be considered as a type of AI and in near future we might have smart contract based on bitcoin blockchain. So simple answer would be yes it is possible to create some sort of artificial intelligence based on blockchain.
Smart contracts are nothing but simple automating bot to automate and process tasks without the need for human interaction still they need to be coded first, you can't tell a smart contract to order pizza and send it to your address if someone never instructed the bot with howtos for getting the nearest fast food shop based on your location and it needs to have access to phone or internet to contact and orders. you'll need to provide your bank account credit card credentials to the bot so it could pay for you as well. all of that is only possible if someone programs a bot to do them, while what is expected from an AI is to do them on it's own
