Q : Do you have to believe in Tradition?
A : Yes, because Tradition hands on a full understanding of God's word. Sacred Tradition together with Sacred Scripture form one sacred deposit of the word of God.
The early Christians learned everything by Tradition, since only later on were some of the teachings of Jesus written down, the last writing being done at the end of the first century.
Q : Are we permitted to believe whatever we want?
A : No, we are obliged to accept all the truths contained in the Bible and Tradition. since this is how God speaks with us as His friends. Saying "No" here is saying "No" to God.
"The Lord Jesus ... will come from heaven with the angels of his power, in flaming fire, to inflict punishment on those who do not know God, and who do. not obey the gospel of our Lord Jesus Christ" [2nd Thessalonians 1:7-8]