Is every linear-time algorithm a streaming algorithm?
For streaming algorithms to be meaningful, they have to work with significantly smaller amount of work space than the input itself.  For example, if you allow the same amount of work space as the input, then you can trivially state any algorithm as a “single-pass streaming algorithm” which first copies the input to the work space in single pass and then only use the work space.

I think that it is typical to restrict the work space to at most polylogarithmic in the input size when talking about streaming algorithms.  Under this assumption, median selection does not have an O(1)-pass streaming algorithm by the result of Munro and Paterson [MP80]: any P-pass streaming algorithm for median selection on N elements has to store Ω(N1/P) elements.  On the other hand, median selection has a well-known deterministic linear-time algorithm [BFPRT73].

[BFPRT73] Manuel Blum, Robert W. Floyd, Vaughan Pratt, Ronald L. Rivest, and Robert E. Tarjan.  Time bounds for selection.  Journal of Computer and System Sciences, 7(4):448–461, Aug. 1973.  DOI: 10.1016/S0022-0000(73)80033-9

[MP80] J. Ian Munro and Mike S. Paterson.  Selection and sorting with limited storage.  Theoretical Computer Science, 12(3):315–323, Nov. 1980.  DOI: 10.1016/0304-3975(80)90061-4