1) :) "Employer employee relationship" is a contractual term, which law recognises to be in existance when certain conditions are fulfilled. If you have studied income tax act, especially topics related to salary income, you may appriciate this better.
2) If we are assume that there is a employer employee relationship in appointing trainee, all labour laws like EPF/ESI are applicable to them too.
3) if there is a employer emlyee relationship, then TDS is under section 192B - there is no confusion whatsoever and apply relavant provisions.
4) As far as i know, stipend paid as per Apprentice act, is exempt from TDS and one need to register under this Act and follow the stipulations there in. (I am yet to come accross such registrations)
5) Usually in industry, trainees are not under regular employment and hence it is a contractual understanding and TDS is decuted as per the provisions contained in section 194C. Trainees are not consultants nor professionals. Stipened being a small amount and usually below taxable limit, even 1% is huge TDS and normally refunds are to be claimed.
Best Regards,
Divakar