Switching from T-Mobile to US Mobile: need some help before I commit

Hey everyone, tired of T-Mobile raising my bill so I’m looking at switching to US Mobile. Never used an MVNO before so hoping someone can help.

I want to do the free trial first. I have a number parked at NumberBarn, can I port that in to activate the trial or are some carriers not eligible?

Also can I choose to trial specifically the AT&T network or is it limited to certain networks?

I have 7 lines on T-Mobile but locked in for 4 more months on device payments. Plan is to trial one line now then bring the rest over after. Is that doable?

Last thing, when I do bring all the lines over can I put them on different plans, like one on Unlimited Premium, a couple on Unlimited Starter and the rest on By the Gig? And can some lines be on AT&T while others are on Verizon or T-Mobile within the same account?

Thanks in advance!

Quick update: Mir from US Mobile reached out to me through Reddit chat and got my line set up almost instantly. Genuinely one of the smoothest onboarding experiences I’ve had with any carrier. He also hooked me up with a free 1 month trial which was a nice bonus. Really appreciate the help, Mir, thanks again!