What is the difference between as and like ?Feel free to just provide example sentences.

"like" is for comparing to the way something is (adjectives) or the way something behaves (verbs). For example:

"His face is red like a tomato."
"He kicked the ball like Raúl"

"As" cannot be used in exactly the same way. "As" is also for making comparisons, but it must compare to a full clause. For example:

"His face is red as a tomato is."
"He kicked the ball as Raúl used to do."

In common speech, "as" can sometimes be interchanged with "like," but this is not grammatical and it can sound very unnatural. You example "she is as my sister" sounds very unnatural. In common speech, the verb "is" is often dropped from the end of sentences, making "as" interchangeable with "like." For example:

"His face was red as a tomato (is)"