6.
Now, in the context of factual background of your earlier query covered in Issue ID - 118009, please let me try to answer questions raised by you here:
Question No. 1: Section 50(3) has been amended as interest is payble only on the Wrongly availed and utilised ITC.
Answer: Due to reasons explained in the relevant post/s in issue id - 118009, you are correct in above observations.
Question No. 2: I want to know that if anyone availed ITC and not utilised the same. Is he liable for penalty under section 73 and 74. As there is still a word " avail or utilise".
Answer: Due to reasons explained in the relevant post/s in issue id - 118009, one is liable for penal action either u/s 73 or 74 (depending upon other surrounding facts) against ineligible ITC availed EVEN IF same is not utilized.
Question No. 3: How can we defend to waive off penalty ?
Answer: Considering the entire background of facts as covered in issue id - 118009 and limitation to discuss intricacies of factual issues over forum etc., I would suggest you to take a consultation from a good professional to see if you have got a decent case (if any) to defend or not.
Question No. 4: If anyone has not filed GSTR-9 , however, due date has been gone, Can he take benefit to waive penalty under Section 73 instead of section 74?
Answer: Levy of penalty u/s 73 or 74 has no direct relation with the fact that whether GSTR-9 was filed or not. However, the fact of non-filing of GSTR-9 (presumably, when required) - in itself - cannot be used by you to avoid penalty u/s 74. Actually, if you try this argument, this fact will be used against you by Dept. Penalty u/s 74 can be avoided only if you can prove that ingredients to levy penalty under that section does not exist in a given situation.
Question No. 5: Should department charge penalty u/s 73 instead of section 74 till not filed GSTR 9?
Answer: There is no such obligation cast upon Dept. under law.
These are strictly personal views of mine and the same should not be construed as professional advice / suggestion.