At first, please look at the following sentences.

1)You're (a)as tall (b)as your father. (is tall)
2)She doesn't play (a)as well (b)as her sister. (plays)
3)I haven't known him (a)as long (b)as you ( have known him)
4)He doesn't earn (a)as much (b)as I do. (earn)
5)It's not (a)as hard (b)as I thought.

The those sentences indicate  the expressions of "as~ as".
I want to clearly know for  this expression. That's why I want to ask you something. Please help me.

Q1) The words of (a) like as tall,as well,and so on look "adverb". Right ?

Q2) Then, which part of speech is the second "as" which is (b) as ?  Is it "Adverb" too ? or "Conjunction"  or " Preposition ?  Because there have been some omitted words and a noun or a clause can comes after the second "as", I think (b) as is "conjunction". Am I right ?

Could you teach me about it a little bit ? Thanks in advance.
Wow! Excellent. That is what I want to know. The second "as" can be a preposition and also a conjunction. Thank you so much,Mr.Micawber.