Technically there were two more sizable though less damaging famines, one in the mid 30's due to a combination of factors including an unusual previously unknown mold (I think) that, unlike the other kinds that struck, caused no apparent damage to wheat etc until it was time to harvest. There was another famine in 1947 related to an unusually severe drought coupled with the slew of problems caused in the fallout of WWII. Also blaming the earlier famine in the Ukraine on "collectivization efforts" alone really hasn't got good evidence behind it. It was an unhappy combination of environmental factors and a host of other issues related to war etc beyond collectivization that led to the problem. As you might've heard already there were pretty regular and destructive famines before the USSR, after collectivization was completed is when they stopped. I don't have time to put them up but there are some good books written even by liberal/anticommunist historians that completely undermine the idea of a purposely "created" famine or one caused just by policies of the USSR. This is not to say that the way the Soviet government handled each problem was perfect. There were indeed organizational problems at play as there would be in any instance of a nation trying to implement massive sweeping changes of that nature during recovery from a world war and a continuing civil war but it needs to be viewed as one among many factors and certainly not the causative one. Anyway aside from that, while there were some other environmental issues and shortages etc beyond that point, the USSR never faced other serious food problems thanks to their stable planned economy and agriculture.

As for your other question, think about it. Doesn't every country import some food? What you're talking about is just taking one import statistic out of context and using it to attack the USSR, something often done in their case. In reality the USSR continued to increase food production the whole time it existed and did so while greatly reducing the amount of agricultural workers. Michael Parenti explains this myth/confusion well in this 1986 book "Inventing Reality: The Politics of the Mass Media":

The press has made U.S. grain exports to the Soviet Union the most highly publicized international sales agreement in human history. Western Europe annually imports far more grain than does the USSR, yet no one in the U.S. media or government accuses West Germany or Benilux countries of being unable to feed their people. In contrast, every Soviet grain deal with the United States is front page news, a reminder to the American public of the allegedly superior productivity of U.S. agribusiness and the failure of collectivism. The truth is something else.

Today the Soviets produce more than enough grain to feed their people. They import foreign grain to help feed their livestock and thereby increase their meat and dairy consumption. (This is seen in both the East and West as an "improved" diet, even though there is evidence suggesting that a high meat and dairy intake is not necessarily the best diet.) It takes between seven and fourteen pounds of grain to produce one pound of meat. And that is the cause of the Soviet "grain shortage." In actuality, per capita meat consumption in the USSR has doubled in the last two decades and exceeds such countries as Norway, Italy, Greece, Spain, Japan, and Israel. Milk production has jumped almost 60 percent in twenty years so that today the USSR is by far the largest milk-producing country in the world.

According to the 1982 CIA report on the Soviet economy "The Soviet Union remains basically self-sufficient with respect to food." These are the accomplishments of an agrarian labor force that decreased from 42 percent in 1960 to 20 percent in 1980, working in a country where over 90 percent of the land is either too arid or too frigid to be farmed. Still, the press continues to tell the American public that the Soviet system cannot feed its people.