んじゃなかったか => shouldn't have... N4
Regret
~をきんじえない(~を禁じ得ない) => can't help but; can't refrain from ~ N1
んじゃ => If ... then... N4
Condition (hypothetical condition)
~まじき      => should not; must not N1
んじゃないか => right? isn't it? let's~; confirmation N4
Confirm
~あるまじき => ~ Unacceptable, not allowed N1
Ban
んじゃない => can not, impossible to... N4
Ban
...ようにおもう / かんじる => Looks like ~; Seems like ~; Appears like ~ N3
Evaluate
じゃありません => not to be N5
Emphasize negative meaning
[禁止「きんし」] => Don't do N4
Can, Should, Must
んじゃないだろうか => could it be that ~; might it be that ~ N4
Speculation
~いかんだ / いかんで、~ /  ~いかんによって、~ => It depends ... N1
Related, corresponding