Options In 6th year of H1B with PERM approved but i140 pending

[Simran Ji]

Hi, I am on H1B and below are important dates.

1. Max Out    : Aug 05, 2019 
2. i797 valid : Aug 05, 2019
3. i94  valid : Aug 15, 2019
4. Priority date (PERM) : Mar 25, 2019 <-  Approved on May 30, 2019
5. i140 : To be Filed (Premium Processing) before end of June 2019

Question 1 : Is it a good idea to file COS (H1->H4) now with effective date Aug 16, 2019. So that if i140 is not approved by Aug 15, I can stay here without traveling to India
Question 2 : Considering if COS is approved first and i140 is approved later (let's say someday  in July) 
             2A) Can I file H1B extension for the 7th year based on approved i140 irrespective of approved COS as new status is H4 is w.e.f Aug 16th
             2B) If the answer for 2A is yes (and H1B extension is filed), then for me to continue on work beyond Aug 15th, do I or my employer need to file another COS for H4->H1 in this case or not required.
             2C) Should I inform my employer that I am going to file H1->H4 COS and above situation could occur
Question 3 : Considering if i140 is approved first and COS is still pending
             3A) Can I cancel the COS request electronically and is it immediate.   
             3B) What if COS also gets approved on the same date or next day but after the i140 approval
Question 4 : Would it be a wiser decision to wait for i140 approval until Aug 13th and if not approved, file the COS on Aug 14 (i.e. 1 day before the i94 expiry)  
Question 5 : What will be my last date to file COS (H1->H4). Is it Aug 5th or Aug 15th? I am assuming its Aug 15th. Please confirm