Yes you can apply on your own but with some conditions !!!!!

Information on A card unlimited for Indians

In Brussels/Flanders you can go for unlimited work permit i.e., card A unlimited after 4 years

Single permit has 2 things –> Work Permit + Residing Permit

Work Permit is Approved by Region, and You can work on it.

Residence permit is approved by federal govt based on Work permit, allows us to live in Belgium

So, after 4 years in Brussels region you can apply for unlimited work permit. Which is called as A card with illimite. 

Brussels : https://economy-employment.brussels/single-permit-unlimited

Flanders : https://www.vlaanderen.be/en/work-permits-for-foreign-workers/work-permits-indefinite-term. 

Permanent Residence is when you can work and stay unlimited. So, if you have no job then also you can stay here indefinite

A with limite –> Work permit connected to employer + stay until you work

A with illimite –> Work permit not connected to employer + stay until you work

B/D/L  –> Work and stay unlimited

If my contract is undefined then how the commune will give the end date for the residence permit card ? 1 year validity in Brussels. Unlimited card is 1 year validity and needs to renewby you every year (Like the case before single permit)

In Brussels I know someone(Indian) who applied for unlimited work permit after 3 years of stay in Belgium with Family –> Approved in 1 week apparently

If your spouse, your registered partner or your children are lawfully residing with you: you need to justify three years of employment covered by a single permit or a work permit, over a period of ten years of lawful and uninterrupted residence in Belgium immediately preceding the application.

So, in Brussels there are specific conditions. In Flanders you don’t.

Thanks to Dinesh Varma