Staying in USA on expired I94 using pending "Change of Status" application

[worriedworker]

I was working with employer A on H1 visa. 
I got a job offer from employer B 
Employer B filed for H1 visa transfer petition 
I submitted my resignation to employer A and started working for employer B based on the petition receipt notice. 
After few months USCIS denied my visa transfer petition. 
My spouse is working on an independent H1 visa 
Hence I filed for Change of Status (CoS) to H4 just 1 week prior to my I-94 expiry date. 
Question: 
1) Can i continue to legally stay in US beyond my I-94 expiry based on pending CoS application? 
2) Incase the CoS application gets denied too will i be accruing unlawful presence in USA since my I-94 expiry date? 
3) Employer B is going to file another H1 petition for me through premium processing. Can i withdraw my CoS application if my H1 petition gets approved?