Can I use Lugia VSTAR's "Summoning Star" Ability to put a Colorless Stage 2 Pokemon from my discard pile directly onto my bench?
Yes, Summoning Star can put any Stage of Colorless Pokemon onto the Bench from your discard pile as long as it doesn't have a Rule Box.
Source: Silver Tempest FAQ; TPCi Rules Team (2022-11-10)

Relevant cards

Note: All applicable cards may not be listed below.
SWSH12_139
SWSH12_139