Question: Can anybody suggest me the websites or PDFs from where I can get the meaning and etymology of Classical Arabic terms or any online dictionary of Classical Arabic language or any PDF of that dictionary?

Answer: 
If you want an English-Arabic dictionary for Classical Arabic then I recommend Lane’s lexicon or Hans wehr dictionary.
If you want Classical Arabic dictionaries with only Arabic in it then I have a lot of dictionaries to recommend for you;

1. Lisan al-Arab ( لسان العرب‎)
2. Taj al-arus (تاج العروس)
3. Tahdhib al-Lugha (تهذيب اللغة)
4. Jamhara al-Lugha ( one of the five OLDEST arabic dictionaries in the world.
5. Kitab al-ayn (كتاب العين‎, the OLDEST Arabic dictionary, it is writen in the 8th century)

You really don’t have to worry about the content if these olde dictionaries. I also recommend you to visit <http://arabiclexicon.hawramani.com/> and <https://books.rafed.net/m/> and <http://www.baheth.info/>. These are very good websites.
try <http://lex.sibawayhi.org>

it's a little rough but it contains the full text of both Lane and Lisaan al-Arab, in parallel. 

It's not designed as a dictionary, i.e. something where you just look up a "word". It's a tool for exploring the lexicon. it only understands roots, and will show you all permutations for a root, so you can examine Eg all words that start with "kt" and ponder whether they share a common semantic kernel - a very old theory in Arabic lexicology. you need to read the help screen carefully and experiment. E.g. Lane and the Lisaan pick different roots for some words that have "weak" letters, and I have not yet unified them.