Hi @Naila_Nosheen,
I don’t understand what isn’t sorted in your output. Each lookup adds a new array of documents that come from a different collection each time and these arrays are sorted by sequence in each individual array. It’s not what you want?
Do you want to mix all these arrays in a single array where all the questions are mixed and sorted by sequence?
Also please use markdown code blocks when you send code to ease the readability of your posts.