So INFASA takes places After INF:A , where Earth and Mars signed that cease-fire?
No.
Here we go again:
Inferno R1 (INFR1) - Set in 2401, war between the EA and the GTVA, designed for Retail Vanilla FS2.
Inferno SCP (INFSCP) - Complete revamp from INFR1, in a sort of parallel universe but using the same ideas. Also a war between the EA and the GTVA optimized for FSOpen.
Inferno Alliance (INFA) - The early formation of the EA which is set in Sol. Set in 2350. Set in the Inferno SCP continuity.
Inferno Alliance Standalone (INFASA) - Same as INFA, but with a bigger campaign, characters, better plot, etc. etc.
Inferno Alliance II - Another campaign set in Sol. Set after the events of INFASA. Formation of the EA.
Oh, and on a side note. Will both inferno (the early one set in Sol), and the later one, taking place after the 2nd great war, eventually tie in together, or are the both kinda seperate?
Yeah, they will tie in together. INFA is basically the formation of the Earth Alliance (EA), set in Sol, while INFSCP is the war between the EA and the GTVA.