Question Summary:
I am trying to keep my beard to sunnah length, and as I understand it, the minimum requirement is a fist length…

Question Detail:

1) I am trying to keep my beard to sunnah length, and as I understand it, the minimum requirement is a fist length. Is that the recommended length, or is it advisable to keep it as long as it can grow?
2) I know that when performing ghusl, you should wet your beard up-to your chin, the root of the beard, but when performing whudhu, is this necessary or will massah of the beard surfice?
3) I realize the following question seems silly, but I have been asked by some friends and was never able to answerer it to my satisfaction as I have always been confused by the use of the following terminology:

a. Farth: I understand this to be compulsory and sinfull if neglected
b. Waajib: I understand this too to be compulsory. Is it too sinfull if neglected? How is it different to the farth?
c. Sunnah: I understand this to be the practice of our beloved Rasoolulah Sallalahu Allayhi Wasallam. Many imams have told me it is sinfull to neglect the sunnah. Is this so? If it is, how is it different to farth.
d. Wirt salaah in esha. What is the status thereof and is it sinfull to neglect.
e. Makrooh: I understand makrooh to mean reprehensible. Does this mean a makrooh act is sinfull? If so how does it differ to a haraam act?

Answer :

In the name of Allah, Most Gracious, Most Merciful
Assalaamu `alaykum waRahmatullahi Wabarakatoh
1. The minimum requirement for a beard is a fist length. After that, an individual is at liberty to grow his beard even longer is he wishes to. Ibn Umar (RA) used to trim his beard until fist length.
2. If the hair is so thick that the skin cannot be seen, then it is not compulsory to wash that skin which is hidden. That hair is actually in place of the skin. To pour water over it is sufficient. (Behishti Zewar, Vol 1, pg 53)
3. Farz and wajib are both compulsory. A farz is deduced from a source that is Qatiyyus Suboot (absolutely proven) and Qatiyyud Dalalah (absolutely understood). A wajib act is zanni (not absolute) in one of the above two. It is either not absolutely proven but absolutely understood or vice versa. This is mainly an academic discussion. For simple understanding and practical purposes, both are referred to as compulsory in shariah. Academics understand that the level of compulsion between them is different.
There are two types of sunnats- sunnat-e-muakkadah sunnat-e-ghair muakkadah. Muakkadah refers to emphasized sunnah. This is understood from the consistent practice of Rasulullah (صلى الله عليه وسلم) in those issues, for example, the sunnats before Fajr salah. If one leaves out a sunnah muakkadah, it will be a sin. Sunnah ghair muakkadah are those practices which were not practiced with such consistency as sunnat-e-muakkadah acts, for example, salatud Duhaa (chaast salah). If one carries out such sunnats, he will be greatly rewarded. If he does not carry out those acts, he will not be sinful. However, shariah has emphasized on following the sunnah of Rasulullah (صلى الله عليه وسلم) as closely as possible. To show disregard to any sunnah is against the spirit of Islam
Witr salaah is wajib.
If one commits a makrooh act, it will constitute a sin. 
And Allah knows best
Wassalam
Mufti Ebrahim Desai
Darul Iftaa, Madrassah In'aamiyyah