你的句子用倒装，与句首的 only 有关。你应该知道，“only+状语”置于句首时，其后的句子是要用部分倒装的。比如：Only in this way can we learn English. 只有这样才能学会英语。Only by shouting was he able to make himself heard. 他只有叫喊才能让别人听到他。Only then did I understand what she meant. 只有到那时我才明白她的意思。Only when he is selfless can a man be fearless. 只有无私，才能无畏。Only if a teacher has given permission is a student allowed to enterthis room. 只有得到教师的允许，学生才可以进这间屋。在网友的句子中，only 后面接的状语是 once these requirements arefully satisfied（这是由once引导的时间状语从句），所以后面的 is 要提前变成部分倒装。