I want to know if its ok to install a juction box and then extend the wire for my electric range in order to move it to the new main panel we installed, rather than installing a new run right from the range (its a long ways). I know the juction box has to remain accessible but are there other issues with doing it this way?
In the US you would need to run a 4 wire cable (2 hots, neutral, ground) to the new location. If that is what exists in your current run, no problem to splice in a j-box and continue the run. If it's only a 3 wire cable, you need to go back to the panel.
If you do splice, use an insulated splice "boot" rather than wire nuts or split bolts. Polaris is a brand we can get here.
Hopefully some Canadian will chime in if there are different issues in B.C.