These are not "modal verbs," but rather "phrasal verbs." Modal verbs are verbs that change the "mood" of the sentence and can be any one of the following: can, could, may, might, must, should, shall, will, or would. Phrasal verbs, however, are verbs combined with another word to create a new meaning and treated as one unit. When I say that they are treated as one unit, I mean that you should treat, for example, the phrasal verb "add up" as one verb. Don't think of the two words individually and what they mean individually, but rather think of them as they are together. "Add up" has nothing to do with anything going "up," it simply means to determine the sum of a given object. So, "Can you add up all the cards" is a polite request to "count all the cards" or "find the sum of all the cards." In phrasal verbs, the placement of the noun (whether it goes inside or outside of the phrasal verb) doesn't matter UNLESS it is a pronoun: I will use your second example to demonstrate: "You can bring your friends along to the party." OR "You can bring along your friends to the party." Both of these options are fine, but let's see what happens if you change "your friends" to a pronoun. Since it is plural, the pronoun will be "them." "You can bring them along to the party." *correct* "You can bring along them to the party." *incorrect* If the object of the phrasal verb is a pronoun, then is MUST go inside the phrasal verb, that is, between the two words that create the phrasal verb. Sorry for the long explanation, but I wanted to give as much detail as possible. If you have any other questions or are still confused, please let me know.

I'd just like to add to Lee's great answer on phrasal verbs. There is no fixed rule which covers all phrasal verbs. The type of phrasal verb you are talking about is a "separable phrasal verb". You simply have to learn these as you go, and remember that the meaning can change if you treat the phrasal verb as separable or inseparable. Both of your examples are separable: "add up the cards / add the cards up"; "bring along your friends / bring your friends along". If you use "them", then the rule is exactly as Lee described. Also, you would not put the noun into the separable phrasal verb when you have a long noun clause, or it's tagged with relative clauses. That would simply be confusing. For example, if you write "bring your friends who I met while out last night and had a great time with along", then by the time we see the word "along", we've already forgotten why it was needed. ;)

The answer to this is actually way easier than you're expecting. Ready? It's entirely up to you. You can choose how you like to speak. Here's what I mean: Your first example can also be written as "Can you add all the cards up?" See? It means exactly the same thing, but now the noun is between the two parts of the verb. Similarly, your second example can also be written as "You can bring along your friends to the party." I'd suggest you just learn one way to say each of your two examples, since they both mean the same thing. Good luck!

In English, to ask any question, you must invert the word order of the subject and the first verb. If the first verb isn't a modal verb however, you must add "do" first. E.g. "I can..." => "Can I...?" "You will..." => "Will you...?" "I see..." = "I do see..." => "Do I see...?" "See" is not a modal verb, so "do" must be added before making it a question.