[SalesForce] How to extract Name from id,which a Lookup field catches

I think you can do something like this:

Schema.DescribeFieldResult f = fieldsMap.get(field).getDescribe();   
System.debug(f.getRelationshipName())    
for(Schema.SObjectType reference : f.getReferenceTo())
{
    System.debug(reference.getDescribe().getName());
}

See docs here for more info.

While lookup and master-detail fields are supported, this is only in terms of being able to reference a value from another field. So I have a scenario where an account can only have opportunities with a specific pricebook, so I have populated a lookup to the pricebook on the account object. I can then predefine the pricebook on a "new opportunity" publisher action with the following formula:

Account.Price_Book__c

Unfortunately you can't pass in the id of a specific record as a literal.