regarding copyright

1) Yes

2) No

Basically that is what stock is for. You licence items (also from the free collection) for commercial and non-commercial use and you can modify the asset as you need, with some exceptions (ex: you can't use these assets for the tripple X sector). 

Please note that ther are different licencing level (Standard, Extended, Enhanced) and depending on the use you have, you may need one or the other. However, all licences allow for 1).

Look here for more information on licensing: https://community.adobe.com/t5/stock/links-for-licensing-terms/td-p/11366788
(Disclaimer: As always with licensing, this is my interpretation of the rules. I think they are correct and advice is based on reading and interpreting the licence terms and on fair use for both the buyer and the artist/stock company, but I cannot rule out that my interpretation is wrong. I'm not an Adobe employee).

Perhaps this link will be of assistance:

https://helpx.adobe.com/stock/kb/adobe-stock-known-issues.html#:~:text=You%20can%27t%20use%20Adobe,it%20doesn%27t%20transfer%20copyright.