No. Long Stay ('authorisation for provisional stay' or 'family reunification') takes precedence over Short Stay.
Yes, the conditions for entry into the Schengen Area are the same for all third-country nationals, whether or not they are subject to visa requirements for short stays.
De Council regulation (EC) No 539/2001 of 15 March 2001 listing the third countries whose nationals must be in possession of visas when crossing the external borders and those whose nationals are exempt from that requirement.
You can access European Union law via the site https://eur-lex.europa.eu
You must show that you personally have at least 45 euros per day for staying with friends or relatives and 95 euros per day for staying in a hotel. The following can be accepted as proof: traveller's cheques, credit card or cash.
If you do not have sufficient personal resources, you may rely upon a guarantor who must complete a dependents form (annex 3bis).
No, unless this visa was issued to marry or to declare a legal cohabitation in Belgium.
For long stays, you must enter Belgium with a D visa (residence permit).