Direct proof of use
Armament Research Services documented Falaq-1 and Falaq-2 rockets and their launchers in Syria during the civil war. Its May 2014 report says the combat application of Falaq and Falaq-like systems in Syria appears to have begun with government-force use, first documented in videos toward the end of 2012.
The same report identifies Falaq-1 type launchers in man-portable single-tube, two-tube towed, and four-tube or six-tube vehicle-mounted configurations. It says those Falaq-1 type launchers appeared with Syrian government forces, including the Syrian Arab Army and National Defense Force, and with Jabhat al-Nusra.
Sources: Iranian Falaq-1 and Falaq-2 Rockets in Syria
Timeline
ARES dates the first clear picture of a two-tube Falaq launcher in Syria to early November 2012 in Aleppo. The report also describes earlier late-2012 videos as the first documented evidence of government-force use.
By May 2014, ARES had cataloged several Falaq-1 type launcher forms in Syria and attributed observed use to both pro-government forces and Jabhat al-Nusra.
Sources: Iranian Falaq-1 and Falaq-2 Rockets in Syria
Narrative
In Syrian service, the Falaq-1 appeared as a short-range rocket-artillery weapon rather than as a standardized battery system. The documented launcher set included portable, towed, and vehicle-mounted arrangements, which suited the fragmented ground war and the report's description of dense urban fighting.
The available source separates original Iranian-made Falaq systems from Syrian Falaq-like copies and non-standard rockets that could be fired from Falaq-1 type launchers. For this record, the direct usage claim is limited to Falaq-1 type launchers documented in Syria and the actors ARES identified with those systems.
Sources: Iranian Falaq-1 and Falaq-2 Rockets in Syria