This is regarding UK England. I don't know much about taxes and wanting
some more help and advice.

I understand that the PAYE tax rate is 22%?

Is it true that one can reclaim his tax payments back for a tax year if
he earned less than 10,000 during that tax year. Is it correct that
it's to do with how much one earned during that tax year, and not how
much you would've earned if you worked for a whole tax year?

Why is my National Insurance contributions different each month? I
understand that NI is for NHS and entitles one to NHS hospital
treatment. However, is the amount each month related to how much that
person used NHS services? So if you go to the doctors/hospital regulary
then you get higher NI contributions?

A friend told me he got tax discount (3 months of low tax pay) when he
first started his job. He was a student then got a job and stopped
studies. I never got this when I graduated and got a job immediately
afterwards. Is this right?