1st question: By default, if a reviewer and/or approver is not selected, the request is routed back to the submitter. We do not want that, so is there anyway to make it mandatory that the boxes must be manually checked before submitting? I know we can enter users under the promotion reviewer and approver roles so they will appear automatically, but we want to manually select the users because they will be different users depending on the request.
2nd question: We have a customized workflow where it goes to reviewer first, the reviewer must accept or rework or reject. If accept, it routes to approver. As you see per below, we have 4 columns, we want only 2 columns per (OOTB). We have removed the Promotion Reviewers and Promoton Approvers roles with the Context Team to see if that would do the trick, but no luck.................Any suggestion on how to remove Approver and Reviewer columns?
Within the workflow, I can click remove the Approver and Reviewer, but it always comes back.
Great mysteries... But very satisfying when you figure out (incrementally) how to make it do what you want 
Do yourself a favor for this and get back to the OTB condition, then methodically make modifications to see where they have effect (I did this in detail lots of times to be able to master this area - complex how all elements interact but flexible because of it):
1. Use a non-production Windchill system
2. Create a Product or Library context and strip out all the Roles except Promotion Approvers and Promotion Reviewers; start with them empty
3. Strip the Promotion Request workflow down to the minimum
4. Reset the preference "Fixed Roles For Promote" at Site level and delete child instances
5. Make sure that Promotion Request OIR is using the OTB site level OIR (disable any at Org or below) - uses "Promotion Request Team"
6. Make sure that the Site level Promotion Request Team has the OTB roles: Approver, Reviewer, Owner and that they are not populated; disable / delete any Promotion Request Team at Org or lower
7. Start methodically working with it in this condition
8. New Prom Req wizard will show the minimum. Pause, add users to the context team, refresh the wizard, and you immediately see them populated
9. More here, but have to run to a meeting...
note: Can also create a bunch of prom req workflow templates, and list them all in the Promotion Preference Management setting, then easily switch between them in the New Prom Req wizard - saves a lot of time
