Are these sentences OK?
I can walk myself. / I can go down the stairs myself. / I can go up the stairs myself. (a patient etc.)
That reminds me something I heard before. / That reminds me something I saw before.

Question

Are these sentences OK?
I can walk myself. / I can go down the stairs myself.  /  I can go up the stairs myself.   (a patient etc.)
That reminds me something I heard before. / That reminds me something I saw before.

Answer

I can walk BY myself. / I can go down the stairs BY myself. / I can go up the stairs BY myself. (a patient etc.)
That reminds me OF something I heard before. / That reminds me OF something I saw before.

Answer

1. More typically: I can walk by myself. or I can walk on my own.
2 + 3 are fine.
4. That reminds me of something I heard before.
5. That reminds me of something I saw before.

Answer

The first three sentences are correct however, the second set of sentences should be "that reminds me of something I have heard before./ that reminds me of something I have seen before." Your version of "saw", while past tense, is not proper grammar.