PIP Tribunal date need to change it

The Tribunal date for PIP is set on 4 April 2017. I am mostly homebound/'bedbound. Had higher DLA rates for care and mobility. PIP removed my higher mobility rate (ex GP prescribed a wheelchair for mobility issues and heart failure), and awarded standard care rate. I am waiting to be assessed by social worker for care package because I moved LA.
I am unable to attend because:

1. Awaiting tests results from neurologist and cardiologist and waiting for more tests.
2. Carer is unable to come that day.
3. Welfare adviser is busy, not met yet to prepare for the redress of lies from Atos
Assessor.
4. Will have care package assessment within the next week or so.
5. Not ready,not been able to even look at the papers from refused MR since November
and feeling rather unwell. Unable to even look at the lies from the Atos assessor,
nauseating. Felt traumatized by the deviousness, the lies, and exaggerations.
6. Welfare adviser is too busy at the mo, he is unavailable till 22 ~March, but for a brief
tel con, then will fit me in for a longer appointment.

I do not expect my new GP to write a supportive letter on my behalf, she is on extended leave. Which is the best choice below:

1. Could they refuse to change the date on those grounds?
2. If they do refuse. Do I not appear, on 4th April, then appeal on the grounds I was unable
to prepare for the case in time citing the reasons as above in the first para?
3. Do I try and rush preparing for it, but won't be adequate, then appeal if not in my fabvour?
4. Or ??????
Thank you.

Thank you Gordon. Should I mention that the hearing went ahead
in my absence because I am unable to turn because of lack of support
it would be classed as an Error of Law?

Also, will the hearing strictly adhere to all the evidence I sent, but not on recent diagnosis of two weeks ago by a neurologist which evidenced all the symptoms I described.

In otherwords, I described the symptoms when I applied for PIP, but it was not diagnosed.

As for mobility, I was referred by my ex GP, who wrote mobility difficulties and heart failure. The OT expanded with vertigo, drops in bp, etc.. It was discarded by PIP for the MR. They said I sent it too late. I did however tell the assessor my wheelchair was prescribed by ex gp and ot. Can I use the evidence now that finally the ex GP and ex OT sent their reports?