B2 Visa Extension denied

[JpJinu]

I am 27 years old, in USA on B2 visa since March 2020. I applied 1st extension on 8th Aug 2020 before I-94 expiration(19th sept 2020). I applied second extension on 9th Feb 2021 and had my fingerprints done on 7th April 2021. I received the denial notice for 1st extension on 12th April 2021 (Notice date is 1st April 2021). The reason of denial is that I submitted the I-539 form as a co-applicant of my mother whereas the correct way was to file it separately.
Can anyone help me with below questions.
1. Does the denial of 1st extension matters when the 2nd extension is in progress and fingerprints were taken? USCIS site still shows "Fingerprints taken" for both the extensions.
2. Do I get 30 days grace period for travel arrangement or I've to travel immediately back to India? I have 2nd dose of COVID appt. on 24th of April and planning to travel after that.
3. Does the grace period time is considered as a un-authorized stay? Does my B2 visa already got cancelled? How will I come to know about the status of it?
4. I am planning to apply for H1/L1 next year, will this impact on the new filing?
5. Does anyone know how to make corrections in already submitted I-539 form as I made the same mistake in 2nd form as well?
6. Can I seek help from Attorney and apply for motion to reconsider my case?

Thanks in Advance.

[newacct]

1. Yes. If the first extension is denied, that means the second extension was not filed while in status, so it will almost certainly be denied, and the second extension will also not protect you from accruing unlawful presence while it is pending. So unlawful presence will accrue from the date of denial of the first extension.
2. I'm not sure what you mean by "grace period". You accrue unlawful presence immediately from the date of denial of the first extension. What you may be referring to is the policy where they will usually wait until 33 days after the date of denial before issuing you Notices to Appear for removal proceedings.
3. Yes, the visa you used to enter the US is already automatically void under INA 222(g), since you were still in the US on the date of the denial.
4. There is no ban as long as you do not get put into removal proceedings, and you leave the US before accruing 180 days of unlawful presence. Other than that, it's hard to say whether there is any "impact".
5. Like I said, the second extension was not filed while in status, and will almost certainly be denied. It's probably best to forget about it and leave the US.

[JpJinu]

Thank you very much Sir, this is really helpful.
1. Is there any way that I will know my B2 got cancelled. I am planning to apply for B2 again in that case.
2. Would you recommend to apply for B2 visa this year after going back to my home country or wait? How long?
3. Do you suggest to provide any documents to USCIS after reaching home country? If yes, what documents will be required?