I'd like to tryout my rule 5 draftees in spring training. If I have room and place them on my ML roster in spring training, can I waive them before the regular season? If I waive them, and no other team claims them, can I send them down to the minors? Likewise, If I keep them on my ML roster at the beginning of the regular season, can I waive them at any time during the season?

Yes, Yes and Yes

If you're making roster decisions on ST stats, you're making a mistake.

Most veteran owners don't use BL players very much. So what your R5 guys are facing is undeveloped prospects. So instead of a 83 control, 72/78 split guy, they're facing 42 control, 47/49 split guy who might PROJECT to a BL player.

Thanks, thanks and thanks. And I concur with your ST advice. I may have an ML roster spot I can "experiment" with by rostering a green R5. If I did choose to waive the R5 draftee after the start of the season, is he still subject to the same process? In other words, If another team claims him, do they need to place him on the ML roster? If no one claims him, does his former team get the option to take him back? Does the former team have to roster him on the ML squad? If no one claims him, I keep him and can send him to the minors? Thanks in advance.

Yes to all.

I think there is one in your 2nd post that is a NO. During the OFFER BACK, the old franchise can take him and it removes his Rule 5 status and he can be demoted. I'm not sure if when he is accepted if he is auto on the 40 or if he comes back off of the 40.

From the Help Manual/GM Basics/Rule 5 Return Accept:
"This will accept a Rule 5 Draft pick back onto your franchise. It will cost $25,000 to do so, but it allows you to bring the player back. This will also clear his Rule 5 status so he can be demoted/assigned without any additional rules in place."