Hello, When "such" is followed by a noun means "type of". For example: We rarely listen to such music. Besides, when "such" is followed by an adjective, you want to give emphasize to the sentence. For example: It is such a beautiful day. On the other hand, "such as" is similar to "like" and they both mean "for example". Therefore, they have different meanings and you can not use one instead of the other.

No, to introduce an example, 'such as' always stays the same.

Not really, "such a" tends to come after the description of something. For example "my dad arrived in a large pink car, such a vehicle hadn't been seen in my street before". "Such as" comes before the description of the subject of the sentence.