Law / researching information for recruiting in Poland [4]

I work for a big company in the UK and I am researching information for recruiting in Poland and wondered if you could direct me on where I might find some of this information out:

• At interview stage – what questions are legal / illegal to ask an individual when being interviewed
• Is it mandatory for companies in Poland to perform Pre-employment checks and if so, what checks
• What documentation is required when recruiting a new employee into a company in Poland (for example – tax forms, certificates of employment, education details)
• In terms of advertising positions in Poland what are the discrimination laws (what a company is legally allowed to request within a job advert – such as specific requirements for the role)

If you can help answer any of these questions or point me in the direction of where I might obtain the information myself I would be most grateful.

Thank you in advance.