1. 阴性血 is use to describe the surface antigen of blood type, which mean RH-negative. 2. 舍姐和同属稀有血型, mean your sister and you has the same rare blood type. 3. 同属 most use to classify two or more items are the same. 像 is use to describe the similarity. 4. 血库告急 Blood bank is short of blood stock. 5. 待 usually mean "a short period of time" or "wait", but in this sentence mean "stay". Complete sentence will be "I wish you can stay here". 6. The sentence is a proverb sentence, which mean "prepared for unexpected needs". For 以备 your may consider as "prepare for". 之需 is a term we don't really use this way. It's easier that you understand the whole term 不時之需, which mean "unexpected needs" or "accident".

I'm not sure I understand your question. But I'll try. "很" represent as "very", so you can put what ever you want to emphasize after it. My answers will be 很好(very good), 很快(very fast), 很小(very small), 很吵(very noisy), 很像(very alike), 很香(the cent smell very good), 很近(very close). Let me know if you need more words.