(Treetop Strand isn't a spell.)
Treetop Strand enters the battlefield tapped.
Treetop Strand is indestructible. (Destroy effects and lethal damage don't destroy it.)
: Add or to your mana pool.
Sacrifice Treetop Strand: Add or to your mana pool.
: Add 
or 
to your mana pool. or to your mana pool.
