Coming Back to the UK from the US for School

I have lived in the UK for eighteen years as a citizen until 2016, when I moved to America, where I am also a citizen. Now, I am 21 and wish to return to the UK to go back to university. I have my passports and housing will not be a problem, as my mother still lives in England, but I'm worried about student finance, will i still be able to receive it if I haven't lived in England for two full tax tears, what are my entitlements here?

It isn't about 'tax years'. You need 3 years residence.

https://www.gov.uk/student-finance/who-qualifies

Your nationality or residency status
You can apply if all of the following apply:

you’re a UK national or have ‘settled status’ (no restrictions on how long you can stay)
you normally live in England
you’ve been living in the UK, the Channel Islands or the Isle of Man for 3 years before starting your course