Help understanding some corrections on my sentences made using あげる、くれる, もらう

Question

my japanese friend corrected some sentences I made and unfortunately can't speak the greatest english so I was looking for some explanation. I made the following sentences. I recently learned about て＋あげる、くれる、もらう and so I set out to make some sentences.

1. 毎朝、犬にボールを持ってくれました -> 毎朝, 犬はボールを持ってきてくれました

The right is the correction she made. From my understanding my book says that に marks the person who receives. So my sentence should actually be 毎朝、犬は私にボールを持ってくれました right?

I have not learned the きて grammar after the て form yet, but I looked up briefly an explanation, is it necessary here?

2. 毎朝、犬は私にバボールを持ってもらいました, my friend says this sounds weird and 持ってきてもらいました sounds much better, did I make this sentence correctly?

3. 友達に掃除を手伝ってあげました -> 友達の掃除を手伝ってあげました。 Do we not need to use the に here? To identify that I am doing a favor for my friend by helping him clean?

4. 兄は弟にお金を貸してくれました -> 兄は弟にお金を貸しました. Im not exactly sure whats wrong with this sentence I made. Although her correction makes sense to me.

Answer 1

1. てくる or てきて is divided to て(and) 来る(come)/来て(come). Basically, てくる or てきて means some action and come (to me, here or back here).

So,

犬はボールを持ってきてくれました。
My dog had/got/held a ball and came with it and gave it to me (and I received it).

I think this link is helpful for てくる/てきて.

2. I agree with your friend. It sounds weird.
   I think "毎朝、犬がボールを持ってきてくれます" is the most natural.
   First, 毎朝 is every morning, so past tense "もらいました" is weird.
   Second, きてくれる basically implies "I receive it", so you don't have to say "私に".
   Third, the dog must come to you before he/she gives it to you. So, it is better to say "きてくれる".

3. 手伝う is not used with "に". It means "help something" though help is used for "someone" in English. It is with just を or も. like "彼の仕事を手伝う" or "家事も手伝う".
   It doesn't have two objects at once.
   Then, you need to say "掃除を手伝う" and this cleaning is the friend's task. so you should say "友達の掃除を手伝う".
   If you say "友達に掃除を手伝ってあげると言った。" = "I said that I helped him/her clean.", this sounds natural.
   
   By the way, you might hear a sentence like "彼を手伝う". 彼 is not something, but 彼, in this case, means "彼の何か" (his task). Something he has is omitted.
   
   

4. てくれる(give) basically implies "I receive it" and the "I" is who spoke the sentence except for question sentence.
   In this sentence, 兄は弟にお金を貸してくれました, who said this is someone but the brothers. Besides, this sentence is not question sentence and "お金" is an entity. Therefore, who gets money must be who spoke this sentence, but it must not happens. So, it sounds weird.
   

For example,

兄はお金を貸してくれました
In this case, who gets money is "I" who speaks this sentence.

兄はあなたにお金を貸してくれましたか？
In this case, who gets money is "you", not who asks the question.

By the way, てくれる is not limited to "give something which exists."
For example,

兄は私の荷物を持ってくれた。My brother had/hold my baggage.
In this case, he gives "his behavior like have/hold" to "I".