You can get tm28[dig] in th very left house in the town that you get there if you go through the cave above Rustburo city and keep going north.
you can get 28 dig on route 114
Zigzagoon can be taught Dig at any level once you have TM 28. TM 28 can be found in Route 114.
There is not a tm for bite or crunch.
TM28 Dig in Pokemon R/S is on Route 114 inside the Fossil Maniac's house.
Thunderbolt
Yes, Tm's in Pokemon Omega Ruby and Alpha Sapphire are re-useable
Trade.
Double Team
you can get it in seafloor cavern
25
at the game corner
In the Safari Zone