-Nearly immpossible because of your immigration intent.
如果被拒,以加拿大護照入境,可以入關嗎? 擔心一旦申請 New TN for new company got reject, can't reenter USA.
-You may still come back using 加拿大護照, but you can not work unless you can get H1 status or use EAD, if any.
申請New TN after I-140 approved, 可行嗎?
-No. After submission of I-140 the TN holder may no longer be able to renew or get his/her TN visa because submission of I-140 manifests immigration intent. So, you may ask your company to sponsor your h1 status.