This is a surprisingly complicated question and somewhat depends on context. In general, though, "you didn't feel" is more of a one-time thing (in the past), along the lines of "You didn't feel happy when we threw you a surprise party," while "you hadn't felt" is more of a state of being (also in the past), like "You hadn't felt scared for a long time."

Honestly, a lot of this depends on context. Some of these could also be different tenses, as you can see by the differences between my and Certainly's responses. - while Clarke (left) the newsroom Lois (called) the police [I put this in past tense, Certainly used present] - salima we (thought of naming) the baby rawia what (do you think about) that name - it's (sounding) pretty [This is different because it's = it is, and the tense is basically already given, although this is not a common phrase] - please do not forget (to book) a chair for me next to you in the cinema tomorrow [I agree with certainly – it makes more sense to say save in this context] - May (has taken) photos ever since her parents (bought) her a snapshots of friends and family but then she (changed) to black and white - lately she (has shot) a lot of nature photographs [once again, I used a different tense than Certainly] - I'm writing this letter (to express) my anger and disappointment at (having) fast-food chains in the dining halls [This just flows better than Certainly's version]

Using as in the context of your first sentence makes sense! Another way to say it would be "does it need to be marked like as shown in the drawing?" but either way is acceptable.

Basically: The rules for cooking plaintains using this method (whatever it is, there's no context to tell us what method) is the same for cooking the other greens. [The first part of this second sentence makes little to no sense without more context] Make sure that these (the other greens) are cooked until tender (soft) and slightly crisp (crunchy).

"Just" is used as an adverb (to describe an adjective or a verb) and it has the same meaning as "only" in that context. For example: She was only twelve when she won her first national science fair. In this sentence "only" can be replaced by "just" and the sentence will still have the same meaning. "Only" can also be used as an adjective, in which case it means that there is one of whatever it is you're talking about. For example: This is the only key to the door. "Alone" means that an object is by itself. (She was alone in the room.) You can change the way these sentences are written to use any of the above words. So instead of saying "She was alone in the room" you could also say "It was just her in the room" or "She was the only one in the room" I hope this wasn't too confusing! (Note, the above is my attempt at condensing the following link, which explains the difference between "just" and "only" much better than I do: http://www.ecenglish.com/learnenglish/lessons/only-and-just I don't really have any links explaining the difference between all three of them, though).