2. I understand that full nodes verify every transaction in the blockchain, but how is it done and if light nodes do it too, how they do it if they don't have the full copy of the blockchain?
They don't and they don't have to.Any bitcoin-related software capable of creating, receiving and broadcasting transactions is technically a node, that is, it can be considered a part of bitcoin network. Despite the fact that light nodes are limited in their ability to verify validity of data coming from other node, they still play a very important role of providing mobile communication for bitcoin users. The only thing you need to spin up a light node is minimum hardware and working internet connection. You can have thousands of light nodes for no additional cost in terms of storage or bandwidth. You can create your network of nodes in which all light nodes will be connected to your own full node, and that will allow you to transact from any part of the world without having to rely on third-party solutions. In fact, without light nodes, the adoption of bitcoin technology is impossible because not all people are going to run personal servers with bitcoin software installed, most of them will be connecting to Uncle Jim's server, whom they fully trust.
