Urgent help needed for changing b2 to R 1

[navyguy]

I'm currently in the USA and I'm about to apply for Changing my B2 to R1as i'm qulified for this and I got a job offer , My qustion is , My employer is tax exmpted, do they still have to provide IRS transcrip or filing ? or just the determination irs letter would be enough ??? and what if the processing is late can I still extend my B2 or no .. and if there is any advice please let me know .. thank you so much