This question has two distinct components.
At what point did the Civil War become inevitable?
The Civil War came about as the result of a slow-moving sequence of events that led to a disastrous result. However, the point of inevitability occurred several decades before the actual outbreak of hostilities.
The 1828 Tariff of Abominations, enacted with overwhelming support of Northern representatives in the US Congress, placed an exorbitant tariff on the importation of goods from abroad. This adversely impacted the South's export-dependent agrarian economy. In response, South Carolina declared it would not enforce the tariffs within its own borders. Rather than immediately respond with force, as it threatened, the United States government slashed the tariff rate, substantially surrendering to South Carolina's demands. Though, on the surface, this had the appearance of compromise, it also signaled to the South that the federal government was not serious about the use of military force against states transgressing federal law.
Instead of capitulating to Southern demands, had the United States insisted on enforcement of the 1828 tariff ordinance, South Carolina might have been dissuaded from announcing its secession in 1860, which precipitated the Battle of Fort Sumter several months later and the onset of conflict. In that sense, the Civil War became inevitable in 1833.
It is said that the Civil War ended slavery, but were the freed African Americans truly free? Why or why not?
While the Emancipation Proclamation legally ended slavery in most areas of the South, it is not necessarily true that it "freed" African Americans. Rather, it set into sequence a series of events that gradually led to the freedom of African Americans.
Following Reconstruction, African Americans faced effective economic and political slavery in Southern states. They were resigned to disenfranchisement through intimidation tactics by extralegal groups such as the Ku Klux Klan and legal tactics like poll taxes. And, despite some attempts at agrarian reform, African Americans remained a largely landless class subject to deprecatory employment conditions.
Later measures such as the Civil Rights Act of 1964, the Fair Housing Act, federal law enforcement intervention to combat groups such as the KKK, and a gradual shift in social attitudes combined to evolve and expand the freedoms envisioned by Lincoln's declaration of 1863 and, two years later, the Thirteenth Amendment.