backdated irESA and SDP to award backdated transitional SDP payment & element

I’ve taken over a client that has had an issue with ESA since 2017 - multiple cases as she’s had to appeal every WCA and PIP decision

Some details are unclear but the timeline is:

Cl is single female with multiple physical and MH conditions (inc bipolar, ADHD, anxiety, dyslexia, dyscalculia)

2017: Cl was getting cbESA with support group

Feb 2017: income for debt case was noted as below - notes state DLA low rate for care and mobility. Subsequent notes show she was awarded PIP later that year - no savings so unsure why irESA was not in payment (potential migration from IB? I’ll need to confirm with cl)

income_category - income_type - period - weekly_amount - monthly_amount
Benefits - Disability Living Allowance, PIP /Attendance Allowance - Weekly - 43.60 - 188.93
Benefits - ESA / Incapacity Ben./ Stat. Sick Pay - Weekly - 109.30 - 473.63
Benefits - Housing Benefit/Local Housing Allowance - Weekly - 92.13 - 399.23
Other Income - Non-dependant contributions - Weekly - 80.00 - 346.67
Pensions - Private or work Pension(s) - Weekly - 10.85 - 47.02

Sept 2017: Cl’s non dependent son moved out

Jan 2018: cl started permitted work and was incorrectly advised she had to claim UC, notes indicate earnings/work/hours were within permitted work - (will need to do a SAR to confirm events) which must have been the case as cbESA was converted to nsESA when she claimed UC that month

May 2018: Cl stopped permitted work due to mental health + ND son moved back in

Sept 2020: ND son moved out

Oct 2020: cl fails both PIP and WCA reassessments - both overturned on appeal LCWRA reinstated and PIP DL standard rate + no mobility

Cl has been chasing SDP payment since 2020, but obviously she didn’t have SDP in payment when she claimed UC so is not entitled

I haven’t spoken to the cl yet so understand a number of mitigating factors could impact the advice but what are the chances of getting irESA backdated to 2017? If she did have SDP when she claimed UC would the son moving back in impact eligibility for the transitional SDP payment (before converted to the element)?

Previous advisers have written to ESA detailing most of above asking for her claim to be looked at (April 2021) - cl states there has been no response