When you ask an SDA what is it they believe, you will typically get a myriad of answers.

Ask for the document that lists exactly what someone who want's to become a member must believe.

If you press for what makes Adventistim distinct from Evangelical Christianity, you will begin to hear--three, sometimes four--distinct and unique SDA teachings.  They are referred to by different names within Adventist Circles but what I knew them as are in bold italics

• The Investigative Judgment / Heavenly Sanctuary aka Great Disappointment
• The Jewish Sabbath Observance aka Seal of God
• (S)pirit of (P)rophecy aka Ellen G White
• Soul Sleep aka State of the Dead

Regardless how these are called, these four are the doctrines where they stand out from Orthodox Christianity.

Ask an Adventist what their Official Creed is or from what do they catechize their members. You will get different answers. In my personal search for the Adventist Catechism or Creed I spoke with Elders, Conference & Union Offices, Pastors, and even the General Conference of Seventh-day Adventists. The most common answers were--

• The 27 (Now 28) Fundamental Beliefs
• The Baptismal Vows
• There isn't one and
• The Bible is the Only Creed

According to the Seventh-Day Adventist General Conference Ministerial Division the Official SDA Creed is either version of, The Baptismal Vow(s).

Yes, EITHER VERSION. The 13 Covenant or the abridged 3 Covenant Vow. The 13 covenant Vow you find on pages 32-33 of the SDA Church Manual or the abridged 3 covenant alternative vow on page 33. The Fundamental Beliefs are also incorporated by way of specific covenants in the Vows.

See SDA Church Manual Baptismal Vows.

Have you been told you don't have to believe all of them to be Adventist, that you do not have to affirm all of them?  I was informed by the Seventh-Day Adventist General Conference Minesterial Division in the summer of 2009, no you cannot.    If there is any doubt try asking some of these former pastors on this list of names what happened to them.