As I haven't been paying tax as I have been down as part-time all these years with my tax returns and Child Tax Credit claims do I assume I won't be getting the 80% of average profits paid from the Self-Employed Income Support Scheme?

I assume I don't qualify for a thing.  I am already getting barely any work except for 2 hours Monday in a v small hotel locally.

I have received the general email from the government but nothing other than that.

I haven't received the general email I have heard referred to both here and in other places [on the internet], however had a look at the HMRC website this morning. There's a fairly good explanation on there about the scheme

Apart from that it's based on nor to get within 2m of people not in your household as well as enquiries reducing definitely qualifies!!!!

Do you need to do the tax return for 19/20? Like the one you submit in April this year? Just not sure if I have to file that ASAP or can wait.

That's not due until the normal date of Jan 2021 (as far as I'm aware), it's the 18/19 due in January 31st 2020 which I understand is the crucial one.

So by the last 3 years they mean 18/19, 17/18, 16/17, rather than 19/20, 18/19, 17/18?

As I understand it yes  19/20 hasn't even finished yet, I don't think asking everyone to submit their tax returns now would be a great idea. Their systems struggle end of January having given 10 months to do so, and quite a few do submit over that time period. If everyone did it now at once, and on top of everything else I think it would be impossible.

The extended deadline as I understand it is for late submissions from last year.

Taken from the HMRC website from page about help for self-employed;

have submitted your Income Tax Self Assessment tax return for the tax year 2018-19
traded in the tax year 2019-20
are trading when you apply, or would be except for COVID-19
intend to continue to trade in the tax year 2020-21
have lost trading/partnership trading profits due to COVID-19