Are the Russians still using the T-72B as a MBT or just the T-90

The T-72 makes up the majority of their armored force. T-72's are still rolling off the production line.

of course with the T-14 in development due to costs maybe they will stop T-72 production and focus on T-90 and T-14 . Should be interesting to see what they end up doing

Unless I am gravely incorrect, T-72 production of any kind has ceased. Russia is allowing refurb and sale of T-72's currently in stock, but no new production is being done. T-90's are in production, but they are technically not T-72's.

To the best of my knowledge, only the T-90 tank was new production after at least 2008, as only Uralvagonzavod still produces tanks in Russia, all other factories being idled, repurposed, or bankrupt.

But what about T-72B3/B4. Aren't they newly build tanks?

No, upgrades of previous B models.

As for the question about the T-72B still being in use, I think if they are, it is very limited. The active duty tank force has been drastically reduced, to help save rubles, and so much of the bulk of Russia's MBT's were put in controlled storage. They may have a unit of -BV's still in use, for training or low priority defense.

May be they will replace T-62 in MVD units.