H1B to H4 : H4 to H1B Timing

[ImmiQues123]

H1B employment ended with current employer serving 60 day grace period. I have following questions based on the current situation -

1) Can I change status to H4 (my spouse holds valid H1B visa) and come back to H1 right away whenever job is available?

2) What happens if H1B transfer is submitted after 60 days, when I am out of status? 

3) If I submit COS to H4 and while H4 is pending with USCIS, can H1B be transferred to another employer as soon as I have job opportunity? 

4) While H4 application is in pending status with USCIS, and we submit H1B transfer, can I start working on the receipt notice of H1B petition?

5) Are there any concerns when both H4 and H1 transfer are in process? 

6) Once H1B transfer is submitted, do I have to withdraw H4 COS petition?

7) If I have started working with H1B receipt notice (H1B petition still in pending status with USCIS), AND If H4 petition is approved, can I still continue my employment?

8) If I am on approved H4 status, then I find an employment, will I be able to start working on H1B receipt notice? OR do I have to wait until H1B approval? 

9) When H4 is approved, do I need to file COS (H4 to H1B) separately while employer files H1B petition?

Please advice on possible and best action given the situation.