As I mentioned before, the ME-IR just allows you to fly in IFR conditions on any aircraft type that you currently have an active rating on. This rating could be on absolutely anything; MEP or A340 or A320 or B737 or B747 or ..... You get what I am saying here... The 2 ratings are very different, and so their validity will be unrelated.
No true.
The ME IR is broken down into ME-IR-SPA and ME-IR-MPA
SPA = single pilot aircraft
MPA = multi pilot aircraft
If you do it in a single pilot aircraft it's only valid in single pilot aircraft and vice versa.