Your post was pretty difficult to understand, but I guess you are asking if you can use the universal decapper to deprime, then size the brass using the Lee sizing die without the decapping pin? Sure, just use a wrench to loosen the nut on the pin and it will fall right out (make sure to catch it or it might break).
Now, to put the pin back in if need be is a bit more tricky. The Lee design allows the pin to retract inside the die if there is an obstruction in the case, rather than breaking off. If you just put the pin in and tighten the nut all the way, it will not allow it to retract when theres an obstruction (like tumbling media) and you will break your pin. So here is how I put them back in:
1) Place pin till it is flush with the top of the nut and tighten just enough that it doesn't fall out
2) Size a piece of brass, the pin will (should) retract
3) Tighten a little more, and size another piece of brass
4) Continue tightening in slight increments until the pin no longer retracts when you size the brass.