To be honest, your question isn't very clear. But I can tell you this: If a question starts with "Could you...?" it can have at least two possible meanings that I can think of right now. Example 1: Could you open the file? This means, Were you able to open the file? This use of 'could' is the *past tense* form of 'can'. Example 2: Could you please open the door for me? This is a polite way of making a request, this this context, requesting that someone opens the door for you. We like to use 'Could you please...?' when we want to be very polite or when we don't know someone. 'Could you please tell me where the train station is?' Of course, 'could' is also used as a conditional, but the words need to be flipped around: Example 1: Child: "I'm bored." Mother: "You could help me clean the house." The mother is giving her child a suggestion. If he wanted something to do, he could help her clean the house. But as you can see, we have to put the pronoun (you) before the verb in the conditional (could). Since I'm not sure exactly what you wanted to ask, I don't know if any of these explanations are helpful or not.

The question isn't clear. However, the verb "Could" can be used couple of ways. The first one is just the past tense of the verb "can". Example: "I finally could do something yesterday". "I can do today", "I could do yesterday". The following ways of using "could" is using it as an auxiliary (modal) verb. Example 1: "Could I use your phone, please?" here instead of "can I..." you say "could I..." so it becomes way more polite. Example 2: "She could get a good job in that city, if she practices English every day." this is the conditional, cause you have "if"(something could happen, if somebody does something), there is a choice, will she practice English every day, or she won't? Example 3: "I could be wrong, but I think there is a mistake in the context", this a way of telling a possibility, "it's possible that I'm wrong, but I think..." . You don't want to tell directly that something is wrong, cause there is a possibility that it can be right. Example 4: "He could have been a good singer, but they didn't choose him" here it's still a conditional, if something happend, somebody could do something (if they chose him, he could have been a good singer), but it's already in the past, and he can't do anything about it now. I hope it helps Yanyan! :)