It can be but it should be avoided in the projects that uses BizTalk EDI engine as during run time there can be conflicts with this and expected results might not be seen.
Yes, it is possible, both are the ways to utilize already existing schema. The only condition is the schema which is included should have same TargetNamespace or no namespace.
Property schema is a special type of schema, not created to describe messages. Instead, it describes context properties. It consists of only child node under a root node.
It's a node within a BizTalk Server schema that represents the outermost XML element in the business document specified by the schema.
It is a script which when run installs the BizTalk Schema Generator. It is used when generating a schema from existing items. It's likely to get error first time or after updates "WFX to XSD Schema generation module is not installed". Then this script can be used to install the schema generator.
Long running transaction support CD properties of ACID. It is not practical to lock transaction for a long time. This transaction can run indefinitely and can be dehydrated also.
An <Any> element in a schema designates a specific location in the schema where new elements or attributes can be added. When BizTalk uses the schema to process a message containing unknown elements or attributes in the designated location, the schema will still consider the message valid.
Correlation types define a set of properties on which you will be correlating messages. These can be any properties which were previously defined in a property and deployed with some BizTalk Project including "system" properties deployed with the GlobalPropertySchemas Jump which is installed as part of the base BizTalk install. A correlation set defines a set of properties and values for these properties that a message must contain to be processed by a particular orchestration.
BizTalk uses a combination of namespace#rootnode to define the schema type of a message, thereby making a MessageType unique (for example: http://mynamespace.com#MyRootNode). In other words, BizTalk uses this combination to identify and resolve schemas references.
An Orchestration can have more than one instance running simultaneously. Even though each of those multiple instances perform the same action, it does it on different data contained within a message. Correlation is a process of associating an incoming message with the appropriate instance of an orchestration. For Example: If your orchestration issues a purchase order, receives an invoice, and sends a payment, the developer must make certain that the invoice message is received by the orchestration instance which corresponds to the orchestration that sent the Purchase Order. Without correlation, it would be possible to send out an invoice for thousands of items even though the purchase order is for one.