How and Why should I apply for EU Blue Card?

Hi, I am looking for guidance on EU blue card - its benefits and process to apply.
I am working as a business professional in a Polish division of an India headquartered company. I am based in Poland since 2014 and working on an indefinite term employer contract but a company sponsored TRC (temporary residence card) with my family. Of course, my company has never tried to get me EU Blue card as they would not like me to work with any other company in Europe. But I am looking for alternative options and therefore exploring EU Blue card. I meet the minimum salary expectations for its application.

Now, my questions are following:

1.) How do I apply for EU Blue card, given that I already have a company sponsored work permit and TRC?
2.) Would I be eligible to look for job elsewhere, if I get a EU Blue Card?
3.) Do I have to obtain some documents from my employer, besides the employment contract, that I already have.
4.) If I get an EU Blue card and find a job elsewhere, would my new employer have to apply for my TRC in that country or would I have to do it myself and if I would be eligible for that?

Looking for above information.

Regards,
Rohit