I am new to this Block Chain environment and this is not an excuse for asking this basic doubt its just that I am very curious about this question and I am not able to find any answer to this question. The questions are:
1.) What is the functionality of the node. What I have understood by far is that a node has to find the solution of a question and if some node finds the solution(nonce) to the question that block gets mined. Does this process happen in any form of consensus for example does this also happen in the proof of stake?
2.) Does the node validate the transaction(validate in the sense that it checks if the user is capable of spending the requested amount of token which they have requested) and also solve the tough question provided by the block chain to get the solution(nonce) in order to mine a block in the block chain?
3.) What if I want to make a decentralised twitter, will the users have to pay money to send any message on it? Because according to my learnings so far each block has to mined and it will need some gas to be mined, so why would anyone shift to block chain if that thing is free in centralised network
4.) When I as a user am making any transaction on the block chain,for instance I am sending money to some one else, then I am interacting with the smart contract right? so how would the node know which smart contract should be executed because there might be many contracts on that node isn't it?