[CzechTexan]

Tex
This map is in 409b1m.
If I download this map and install into 409m will players be able play missions I have made in the 409b1m Vs. even if they don't have this map? Or will no players be able to join this mission unless they have this map installed into 409m.
Rudder

If I understand your question right, all players must be using AAA MODS and have this map installed.
This is a MOD map using AAA MODS file structure and can not be used with the standard IL2 file structure.
So, even though it uses 4.09 objects and 4.09 is needed, you must also use 4.09b1m for AAA MODS.
Hope that answers your question.

On another note:
Thanks to the people who gave us the UI 1.2 this map is now available for easy install with the UI 1.2