Can I use two Devolution Sprays on the same Pokemon in the same turn, to devolve from a Stage 2 to Stage 1 and then to Basic?
Yes, you can.
Source: Dragons Exalted FAQ (2012-08-23), TPCi Rules Team (2012-08-23)

Relevant cards

Note: All applicable cards may not be listed below.
WOTCB1_72