By Parameters.
In Reusable Action1-
Declare - 
name=Parameter ("name")


In Calling Action2-
Call RunAction ["Action1"],name

Here, the Action2 will take value of the variable -name 
from Action1. The conditions are:
Parameter("name")- Should be declared in Reusable Action1.

Yes. you can use data from "Action1" data sheet 
in "Action2" or vice versa.

use DataTable.GetSheet("Action1").GetParameter..... 
in "Action2". (To use data from "Action1" data sheet 
in "Action2")

Yes it's possible.
You have to make one Action as a Reusble Action and call 
that action in your Present action. For example Main one is 
Action1 and Action2 is a reusble action and if you want to 
use the Action2 data in Action1 u have to call like this.

DataTable.Value("name",dtlocalsheet)= DataTable.Value
("name","Action2 [REU_Action2]")

Just in the Action1 give the following :
x=datatable("place","Action2")
msgbox x 

In the Action2 give the following:
y=datatable("name","Action1")
msgbox y 

Just try & see ...i hope we can do it....

if not just let me know ...i will get back to u ...

use global data sheet this enables you to pass the values 
between actions
Assume that there are two actions
1. Action1
2.Action2
 make action 1 as re-usable action and use global data 
sheet for parameteraization
Then Open Action2 and call action1.Automatically action2 
global data sheet is updated with glodal data sheet values 
of action1