I have not played IL-2 in several years and would like to re-install the program.
Prior to "IL-2: 1946" you could stack sequels on top of Forgotten Battles and top them off with content patches. However, the full "1946" release changed that because it came with so much additional content beyond the Forgotten Battles+Aces Expansion Pack+Pacific Fighters+Pe2 Peshka combination of addons that it effectively became the new start point for anybody wanting to use the 4.08m and higher patches.
In other words, if you have a pre-1946 version of IL-2 Sturmovik, Forgotten Battles or Pacific Fighters there is no way you can patch it up to where you can use the new 4.11m patch. You're best and only option is to purchase "IL-2 Sturmovik: 1946" which installs the full anthology of IL-2 content all at once as one complete and singular title, and then sequentially upgrade that version with all of the patches noted by EinsteinEP.