XfinityRewards - Rewardathon $300 back on eligible Xfinity Mobile purchase

This is described as shown below.   Normally, these can be used for multiple purchases, but usually either say 1 time use or for up to 5 phones, etc.   My question is:

1. Can this be used for 300 each phone purchase or just 1 phone purchase?  (it implies this with purchase(s)) and has worked that way on past promotions

2. Are their any restrictions on which phone?  (again, in past it lists those if restrictions and just says phone, so assuming any phone purchased from xfinitymobile)

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PRODUCT BENEFIT

$300 back on an eligible Xfinity Mobile purchase

$300 Visa Prepaid Card