1. I will buy Mom a scarf for her birthday.

(What is the part of speech of 'for her birthday'? Is it an adjective phrase modifying 'scarf', or is it an adverbial phrase modifying 'buy'?

2. Look at the little boy.
(What is a little boy? A young boy or a short boy? Though he is a little boy, he is tall. Can we say like this?)

3. Is sandle called sleepers?
Are sandlas called sleepers?
(Which one is correct? And is 'sandal' a kind of 'sleeper'?)

4. He gave me his heart.
(What is the meaning of this one? Do you have a hidden meaning in this expression?)

1. The prepositional phrase, "for her birthday," is an adverbial phrase modifying buy. It tells WHY you're buying.

2. A "little" boy is a young boy -- generally under age 6 or so. Older boys don't like to be called "little."

3. This doesn't make any sense. A sandal is a kind of shoe.

(Broken Link Removed)

A sleeper has several meanings -- but it's often a pair of pajamas with feet worn by young children.

http://www.prideandjoy.net/images/coccoli%20stripe%20sleeper.jpg

4. "He gave me his heart" means that he loves me.

1. I will buy Mom a scarf for her birthday.

(What is the part of speech of 'for her birthday'? Is it an adjective phrase modifying 'scarf', or is it an adverbial phrase modifying 'buy'?
The prepositional phrase "for her birthday" contains a preposition ("for"), a possessive pronoun ("her") acting as an adjective, modifying the noun ("birthday") which is the object of the preposition. I'd say the prepositional phrase is an adjective phrase, modifying "scarf."

2. Look at the little boy.
(What is a little boy? A young boy or a short boy? Though he is a little boy, he is tall. Can we say like this?)
"A little boy" usually refers to his age, meaning a young boy. Yes, you can refer to a little boy as tall -- implying tall for his age.

3. Is sandle called sleepers?
Are sandlas called sleepers?
(Which one is correct? And is 'sandal' a kind of 'sleeper'?)
I think you mean "sandals" and "slippers." Both are types of footwear; sandals can be worn indoors and out; slippers are usually worn inside the house.

4. He gave me his heart.
(What is the meaning of this one? Do you have a hidden meaning in this expression?)
This expression implies that he loves me. In English, the heart is symbolic of love.
http://www.umich.edu/~umfandsf/symbolismproject/symbolism.html/H/heart.html

1. In the sentence "I will buy Mom a scarf for her birthday," the phrase "for her birthday" is an adverbial phrase modifying the verb "buy." It indicates the purpose or reason for buying the scarf. It answers the question "Why am I buying the scarf?" The phrase doesn't directly modify the noun "scarf," so it is not an adjective phrase.

2. In the sentence "Look at the little boy," the phrase "little boy" typically refers to a young boy. However, the context and additional information can influence the interpretation. If you say "Though he is a little boy, he is tall," it implies that despite being young, he is already quite tall or taller than expected. So, in that context, "little boy" could refer to his age rather than his height.

3. Both sentences are not correct. The correct phrasing would be: "Are sandals called sleepers?" However, it depends on the regional dialect and vocabulary usage. In some places, the term "sleepers" may be used as a colloquial or informal term for sandals. But generally, "sandal" and "sleeper" are not synonymous. A "sandal" is a type of open-toed footwear, while "sleeper" is not a commonly used term for footwear.

4. The sentence "He gave me his heart" is an idiomatic expression that typically means someone deeply or sincerely gave their love or affection to another person. It is often used metaphorically to express strong emotions and feelings of love or devotion. It doesn't have a hidden meaning but is a symbolic statement about emotional attachment.