Was Guinea renamed after gaining independence?

No, Guinea was not renamed after gaining independence. Guinea was previously known as French Guinea while it was a colony of France. After gaining independence from France in 1958, Guinea remained as Guinea and did not change its name.

Which colonizer gave independence to Guinea and who was the prime Minister/president of the colonizer?

Guinea gained independence from France in 1958. The French government, under President Charles de Gaulle, granted independence to Guinea as part of his policy of decolonization in Africa. Sékou Touré, who was a prominent independence leader, became the first President of Guinea following independence.