Information and difference between Eu-Blue card and Single Permit

Hello Friends,

I am Amarnth Staying in Belgium for the past 2.5 years.  I came across the Eu-Blue card which says.
As an Expat after approval of the Eu-Blue card, you can work anywhere in the EU.
My queries are.
1) I have a single permit, which is valid for 3 years. out of which I have completed 1.5 years. Is it possible for me to apply for an Eu-Blue card now? The reason for asking is, I want to change the job and if I want to change then the employer has to provide me a new single permit.
2) Is the Blue card and single permit the same. because when I searched for the process to get a blue card. It navigated for me to get a single permit, which leads me to the confusion of the difference between an Eu-Blue card and a Belgian single permit.
3) If Single permit and Blue card are the same? then canI work in other EU countries?
4) If I have a Single permit that expires in the next 1.5 years then do my new employer need to process a once again single permit in Belgium?
5) If I get an opportunity to work in another Eu country will my residence in Belgian will be considered for PR in another country where in the future I might reside?

Sorry for so many queries.
I had to get clarified?

Regards,
Amarnath