non-EU/critical skills - help understanding stamp 4 process/timeline

[drb2]

I am a non-EU national in Ireland on a critical skills employment permit with stamp 1 IRP card.

Just visited my local garda immigrations office today to renew my stamp 1, I am extremely confused by some of the information I was told by the officer:

1) I was told my stamp 1 cannot be renewed for a full year, but only up till the expiry date on my critical skills visa. As a result it will be expired while I am waiting for my "Request for letter of support for stamp 4" to finish processing.

2) I was told that in this case I can request a letter from DBEI stating that my "request for letter of support" is in processing, present this to garda, pay an additional 300 euro for a short extension to the stamp 1 to allow me to stay in the state while processing.

3) I was additionally told the "21 months of employment in the state" begins not when my employment began, but actually when I received my residence permit, which was 2 months later. This would actually make the 21 months end after my permit expires, requiring me to start the entire process over (new critical skills visa).

Is all of this information true? I could not find anything on the net about them. Not sure if weak google ability or the info really isn't there.

Relevant dates:
Critical Skills Permit Valid: 23/July/2018 to 22/July/2020
IRP issued 03/December/2018 expires 04/December/2019
Employment commenced 01/October/2018

(Critical Skills End Date) - (12 weeks) = 29/April/2020
(Employment Start) + (21 months) = 01/July/2020
(IRP issued) + (21 months) = 04/September/2020

What is the true earliest date I can actually submit my request for support letter? Or am I in case (3) where I'm totally screwed and need a whole new critical skills visa?
Is there really such thing as "letter stating request for support letter is in progress" and if so how do I request one?

Sorry for the very long post, wanted to get all the info in there. Hope someone can help.

Thanks,
Dave