I moved from ON to QC in Autumn. I have two T4 (ON and QC) and one Releve (QC, identical to T4). What do I enter? All T4 and Releve or just ON T4 and QC Releve? Thanks!

You would enter all the slips. If you have a T4 and a Relevé 1 for the same job, you'll enter the T4 first. Then when you go to enter the Relevé 1, then any boxes which are the same as on the T4 will already be filled in using the info you entered on the T4. You just have to fill in any box that wasn't on the T4 (ex: Box E).