• Is for ,isn't a conjuction ?
• Can and be used in every sentences ?

The word 'for' is usually most commonly used as a preposition. For instance, 

• I went to fetch water for my mother;

• She was preparing overnight for her exams, etc.

However, 'for' is also used as a conjunction which can be explained through the following sentence:

• I must stay here, for such is the need of the hour.

No, 'and' cannot be used in every sentence. The application of 'and' as a conjunction can be explained with the help of the following examples:

• She brought three apples and he added two more when he came;

• He would study and I would cook for him.