Applying for Family Reunification on Tourist visa

Only if the partner in Belgium is EU.

The minor child needs to apply from a 3rd country and the biological parent is non EU but legally cohabiting (declared and signed the contract at Gemeente)with a Belgian? Is this still ok?

It is always strongly advised against! They say it's  a longer and complicated route

It will not work as the child is not related to the Belgian partner.
The only thing that you could do is multiple temporary resident permits, but the child will never receive the resident permit (and so if the child leave the country, he'll never be able to come back in Belgium as immigration will see that it was a pain to throw him out of Belgian).

If the Belgian partner is the legal tutor, then it will be doable, else visa request must be done from the home country of the child. (+/- 9 months)

That's the best as Alex has said.

Safe to apply family reunion from the home country of the child.

Yea I understand the psychological stress of waiting to see your child for months, but before you know it it's all over.

Meanwhile get a good and trustworthy child-minder for the child or a trusted relative and call them everyday via wassap, Skype or zoom.

The waiting will be over soon.

Hi! We have the same situation. How’s your application? Did you apply family reunification in yourhome country or change your status in Belgium?