If Voltage determines current , a transformer regulate current?
a transformer can regulate the voltage , increasing and decreasing it .


That's not how we usually describe it.

When we say some circuit regulates a voltage, we mean that it produces the same output voltage, even if the input voltage or the output current changes. Insensitivity to input voltage is called line regulation, and insensitivity to output current is called load regulation.

A transformer doesn't do that. If you change its input voltage, its output voltage will change proportionally (so there's no line regulation at all). If you change its output current, whether the output voltage changes depends on whatever's driving the primary side of the transformer, and how well regulated it is. The transformer doesn't improve the load regulation if you have a poor (high output impedance) source powering its primary.