DLA to PIP 64+

I suffer from both physical and mental health issues and was told to claim PIP in November 2016 when claiming DLA.I was sent the form that same month and submitted it in January 2017 after two extensions. This was disallowed apparently because the return date was Sunday 23 and the form was uploaded on Monday 24.I told that the form would not be submitted for processing, this decision was reversed and I received an invitation to attend an interview. I requested a home visit and was told that the claim was decided on the papers and given enhanced care and 4 points mobility. My MR was turned down with the same result, they seemed to have applied the March 16 regulations to my Mob1 and concluded on no evidence that I can walk 200 metres mob 2. My evidence on the form was that I can walk no more than 20 metres using crutches. I have submitted my appeal and am awaiting the response. I need to know which set of regulations apply, should the pre-March 16 regs apply because the claim was made in November 2016, In which case the Mob 1 is wrong and previous case law applies. Should the Mar 16 regs apply because the decision was made in April ?The simplest argument is to say that my very bad leg has been overlooked and rely on the initial four points awarded in which case if any none zero descriptor applies then I have some mobilty. I suggest that my correct award should be 4+12 =16, or 12+12=24 if I can persuade the tribunal to apply the previous regs. I have no idea how to go about this and whether there has been any case on this, I am 64 and this is likely my last chance to claim PIP mobility.