Step 1: Examine each assumption against the statements.
- (1) "Suffering is because of wants."
The statements say "Desire is the cause of suffering." Since desires and wants are the same in meaning here, this assumption is valid.
- (2) "Life is not always full of suffering."
The statements say "Life has suffering," which does not mean life is completely full of suffering. It only indicates that suffering exists in life. Hence, it can be assumed that life is not \emph{always} suffering. Valid.
- (3) "The eightfold path can reduce suffering."
The statements say "Desire can be reduced by following the noble eightfold path" and "The end of desire is the end of suffering." Therefore, following the path leads to reduction of suffering. Valid.
- (4) "Suffering is caused by life."
The statements attribute suffering to desire, not life itself. So this assumption is invalid.
Step 2: Final Answer.
Thus, the valid assumptions are 1, 2, and 3.
\[
\boxed{\text{Only 1, 2 and 3}}
\]