PIP mandatory reconsideration backdating

I finally got my mandatory reconsideration decision yesterday, and got the award I should have received to start with, getting Enhanced Daily living, and Enhanced mobility, I was on Standard Daily living and Enhanced mobility. I'm really happy with the decision, and it's been awarded for maximum time, which I think is 10 years.

However the award has only been backdated to March 2025 when the original decision of my review was made, I initially received my pip review forms in January 2024, and they received the completed review form in June 2024, after I had to have several extensions due to my medical conditions and how much I struggle with the whole process.
I just want some advice about the backdating of my claim, I have found so much conflicting information on the Internet about when they should backdate my claim to.
When I initially received my pip review forms in January 2024, I was at the time getting together medical information and various letters and evidence to actually do a change of circumstances, but I received the review form in the post before I had a chance to apply for a change in circumstances, as I still had a couple of letters to get, and I was also going to get a independent occupation therapist assessment. I rang DWP and asked them for an extension, and also if it was best to do a change in circumstances or complete the review form, and it was put to me that it would probably be easier for me to complete the review form they sent me, as it would be easier to complete as it's a smaller form, and I also asked about backdating of the claim if I done it as a review, and they said it would be backdated regardless.
Which is why I'm now asking for advice from people on here who will know alot more about the system on here, I rang DWP yesterday and they said backdating it to the original decision date after mandatory reconsideration is correct, I told them what I was told on at least two occasions about the information I was told in terms of backdating when the review form was initially received. Because if I knew it wouldn't be backdated I would of done a change of circumstances from the outset!!
It's not the backdating money alone I'm concerned about, it's the fact my universal credit migration was done in January 2025, and pip has been backdated from March 2025 with the higher award, so I won't receive the extra disability premium on my universal credit award going forwards either, so I will be missing out on that going forwards, which is the main thing I'm concerned about.
The thing I don't understand is all my conditions are exactly the same from when I returned the form in June 2024, if anything I have deteriorated further, as is normal as the majority are life long, progressive conditions, to when the initial decision was made in March 2025, the decision they made was incorrect, with so many false assumptions, and incorrect information, so I paid for a private independent occupational therapy assessment, and I done a mandatory reconsideration and outlined what I didn't agree with from the DWP assessors report, and the only evidence I included was my independent occupation therapy report. I just can't understand why the claim isn't getting backdated to at least June 2024, as even the review form itself they received in June 2024 outlined how much my health had deteriorated since I was initially awarded PIP at the very start, how many more health conditions I now have, and I had submitted over 50 pages of medical letters, scans and reports to support all that.
When I received my report after my telephone assessment she had given me 11 points for daily living, and that has been upgraded to 30 points after mandatory reconsideration, there isnt anything actually changed in terms of my conditions, all I sent them was the occupational therapy assessment report, the big difference is they actually assessed me at home, in my own environment and wrote a report based around the various daily living and mobility components of pip, vs maximus who did a telephone assessment over 3 hours, constantly trying to trip me up, downplay my struggles and health, and write so many things which were both inaccurate and made false assumptions, I recorded the assessment and they said i managed the assessment fine, despite me bursting into tears because of pain and how much I was struggling, which I voiced on several occasions, and I also lost my temper towards the end because I was struggling so much with pain, and the Assessor was just ignoring my request for a break, they literally downplayed everything, my mental health was reported as stable because I have no secondary care support and just see my GP, and my medication for mental health hasn't been changed. I told the Assessor I had been on a waiting list for over a year for secondary care for my mental health, and on waiting list for autism and ADHD assessment, rheumatology assessment, and my medication was been reviewed between GP and Heptology, as my mental health was deteriorating, however I have liver cirrhosis, so medication options etc are very limited, and have to go through heptology department, all of this was totally ignored.
So what are my options now I have done the mandatory reconsideration? I'm happy with the Award level, the length of my award, it's only the backdating I'm unhappy with. If you appeal and go to tribunal does the whole award get looked at? Even though I'm only challenging the backdating, as everything the DWP Assessor and occasional therapy Assessor has been present the whole time since they sent the review paperwork, and to when I returned the paperwork in June 2025, and I was in the process of going to put in a charge of circumstances back in January 2024 when they sent the review form out.
I find it so frustrating because the review form I returned in June 2024 outlined all my medical conditions, how much things had changed, and all my new conditions etc.
And advice would be greatly appreciated, and I apologise in advance for such a long winded explanation of my situation.

Many thanks