Is this sentence correct?

sorry it is not correct you ought to say : this product will be available on Amazon on 20th of June 2014, so you should use "on" instead of "from".

abdelboura, so you should use "on" instead of "from".

No, both are quite common, abdelboura.

can I write 20th June 2014 instead of 20th of June 2014?

yes it is grammatically correct to omitte "of"

faisalkhancan I write 20th June 2014 instead of 20th of June 2014?

You can. You will find dates written in many ways. These are standard:

20 June 2014
June 20, 2014
June 20th, 2014
the 20th of June, 2014

The first two are businesslike.

abdelbourayes it is grammatically correct to omitte "of"

Adelboura;
If you are going to answer questions, please use correct grammar and punctuation. If your answers are full of errors, no one will take you seriously, and you may be subject to moderation.