My guess would be a Caproni ca 100, possibly captured in AOI (Africa Orientale Italiana) and used by the british.
Part one of the question is CORRECT It certainly is a Ca 100! Now how about part two? It has to be easy
If you had had been awake the last time Lawrence of Arabia showed up on cable you would have known he had died in thah bike accident No, not the guy, just the outfit. Think Jaws!
I don't have a reference on british squadron codes so had to resort to google, so it's average-internet-quality info , what I found is GA is 21 (RAAF). RAF Squadron Codes - WWII
Very near miss! You may actually be right (I can't distinguish the two and the photo is not high quality) but my source says it's not a Ju 352.
The 252 is right, the two are very similar externally, the 352 was a "mass producable" 252 but the big red tail band was dropped by the time the 352 was built. Over to you ....