Role change H1B Amendment

Hello

My H1B petition is valid until end of 2019 but my company filed an Amendment due to change of role .I see on the new LCA that the new end date requested is until 2020 .

Question - Is amendment under same level of scrutiny as extension ? In case of a negative decision , will my previous petition date until end of 2019 still be binding and override current decision ?

Legally, am I allowed to withdraw my case if it runs to a RFE ?Please advise .

Thanks

If rejected, you may have to continue on your previous role till 2019 as stated on the original petition before.

And what after 2019? Will I have to file another extension or I ll ve to file for another H1b under non cap ?