Go 5G Plus to Next

Hi all, I currently have 9 lines on 5G Plus (paying $144 before EIP), 5 of which are free due to 3rd line free, BoGo, and free line promos. Over the summer, 4 of my free lines lost eligibility to upgrade on device promos due to T-Mobile policy change. I’m in a spot where I would like to have device promo eligibility on all lines. I am also interested in the flexibility to upgrade annually, and having kids - device trade in “any condition” is a bonus 🤣 I’ve searched in Reddit and can’t seem to find an answer on this. On Next, the legacy free lines become $10/per line, so the calculator was showing me $216/mo. My questions are 1) is this accurate? and 2) Will the free lines at $10 each become eligible for device promos, with the same annual eligibility and “any condition” rules? Thanks in advance for your responses and guidance!