I am afraid that it is not possible to realise on Node level, because what will happend if Node 1 fails? In this case, Node 4 becomes a new active node, but Node 4 could not be an Active and a Standby node at the same time. I think it is possible to do if we are talking about DSN level (using different databases). For example:
Not as such. However an A/S pair can support one or more readonly subscriber datastores. These datastores contain an exact copy of the data in the two master stores but are readonly and you cannot failover to them as easily as you can failover between the masters. You can promote a readonly subscriber to a master but it takes more steps to do so. Readonly subscribers are primarily intended for (a) read scale out and (b) remote disaster recovery. Maybe this will meet your needs?