I would write to get info regarding FoE, is it create trouble when upgrade to NPM 12. Would appreciate if anyone could reply or share their experience or thoughts.
Nope, we have FOE running with NPM12 -- you have to follow the upgrade procedure which is a little tortuous.
You can't run let FOE replicate files until you've upgraded both servers in the pair... but then you've read the manuals and know that
Retrieving data ...