Registering as a sole trader even if net profit for side job is less than 5K

[Redconnect]

Hi all,

I'm a PAYE employee who's looking into earning additional non PAYE income through a side job.

I read on the revenue website that
“You do not need to register for self-assessment if:

• you only have PAYE income
• or
• your taxable non-PAYE income does not exceed €5,000 and your gross non-PAYE income does not exceed €30,000. That income must be coded for PAYE purposes. ’Coded’ means the income is taken into account in calculating your tax credits and standard rate cut-off point for PAYE purposes. In this case, you must submit a Form 12 online through PAYE Services in myAccount.”

1. I assumed that "taxable non-PAYE income" is net profit (i.e. the amount of money left after I deduct the expenses). But someone who works in an accountancy business recently told me they thought this meant "a turnover (not profit) of €5,000". Which one is it? Also, if €5,000 is the turn over rather than net profit limit, then what do revenue mean by "gross non-PAYE income does not exceed €30,000"?
2. I am quite confident I will fall into the second category above as I estimate I will make a loss of up to €1,000 in 2021 and a net profit of less than €1,000 in 2022. I think the main benefit of registering as a sole trader anyway is that it means I will need to complete a Form 11 rather than Form 12 next year, and I can record the loss in 2021 on Form 11 so that I can offset it against the net profit in 2022, but I can’t declare a loss on Form 12. Is that correct?
3. Would I be entitled to Section 82 Relief for Pre-Trading Expenses (e.g. the fees for a relevant training course) even if I didn't register as a sole trader and instead submitted a Form 12 online through PAYE Services in myAccount?

Thanks!