AlwaysON configuration & windows cluster requirements.

Hello,

We currently have AlwaysON setup on 3-node windows cluster for which the details are as below,

SQL Instance-A: (SQL Server 2012 EE)

Node-1 (Active)

Node-2 (Passive)

SQL Instance -C: (Secondary server to host always on databases of Instance-A)

Node-3 (Standalone server which is configured for alwayson for all databases on 'Instance-A')

Now, we are planning to add another 2-nodes (node-4 & node-5) to same existing windows cluster which would be a total of 5-node windows cluster and the details for two new nodes are going to be as below,

SQL Instance-B: (SQL Server 2012 EE)

Node-4 (Acitve)

Node-5 (Passive)

The questions are as below,

1) Is it possible to add 2 new nodes to existing 3 node windows clusterto make  two Active-Passive SQL instances (A & B) and leaving instance-C as it is ? (if possible what would be the pros & cons of such design in production OLTP environment.)

2) Can instance-C be setup with alwaysON  with newly added instance-B ? Basically the whole idea is to share instance-C to have alwaysON setup from instance-A & instance-B.  (if possible what would be the pros & cons of such design in production OLTP environment.)

Thank you.