No 24 Sqn was not a reserve squadron considering the bases it occupied, see below, and the RAF Histories do not mention 24 Reserve Squadron.
24 Sqn arrived in St-Omer and went right to the front at Bertangles Aerodrome in Feb 1916, flying DH2s for 1 1/2 years. From that they transitioned to the ill-fated DH-5 (which implies they had more of a ground-attack role) until Dec 1917. The powers that be took pity on them and assigned them SE5a's in Jan 1918. So, 24 Sq was in the thick of it for most of it.
Britain RFC 24 Hounslow 1 9 1915
Britain RFC 24 St-Omer 7 2 1916
Britain RFC 24 Bertangles 10 2 1916
Britain RFC 24 Chipilly 17 12 1916
Britain RFC 24 Flez 17 4 1917
Britain RFC 24 Baizieux 10 7 1917
Britain RFC 24 Teteghem 23 9 1917
Britain RFC 24 Marieux 24 11 1917
Britain RFC 24 Villers-Bretonneux 30 12 1917
Britain RFC 24 Matigny 26 1 1918
Britain RFC 24 Moreuil 22 3 1918
Britain RFC 24 Bertangles 26 3 1918
Britain RFC 24 Conteville 28 3 1918
Britain RAF 24 Bertangles 14 8 1918
Britain RAF 24 Cappy 8 9 1918
Britain RAF 24 Athies 6 10 1918
Britain RAF 24 Busigny 27 10 1918
Britain RAF 24 Bisseghem 11 11 1918
From:
http://www.raf.mod.uk/squadrons/h24.html
Formed at Hounslow on 21 September 1915, No. 24 Squadron has probably flown more aircraft types than any other RAF squadron. After a five-month work-up, the Squadron moved to France equipped with DH2s. These aircraft were soon outclassed and re-equipment with DH5s followed in May 1917. The Squadron remained in and around the Western Front for the remainder of the War until January 1920 when the unit returned to the UK as a cadre, disbanding on 1 February 1920.