Two brothers we are, great burdens we bear, all day we are bitterly pressed; Yet this I will say - we are full

Question

1.Two brothers we are, great burdens we bear, all day we are bitterly pressed; Yet this I will say - we are full all the day, and empty when we go to rest. What are we?

2.Long and slinky like a trout, never sings till it's guts come out. What is it?

3.Always old, sometimes new, never sad, sometimes blue. Never empty, sometimes full, never pushes, always pulls.

4.I run, though I have no legs to be seen. I possess no heat, yet I do have steam. I have no voice to let words out, but from far away you can still hear me shout. What am I?

Answer 1

1.) Shoes! (or socks)
2.) Accordion
3.) The moon
4.) Train