This app was mentioned in 16 comments, with an average of 0.94 upvotes
LOL, very good.
Don't know how you shot this but if its on an Android phone then you can use VidTrim to rotate the video
Check out Androvid and Vidtrim. Don't know if they can do 1080, but they are worth looking at and playing around with. They both have free and paid (pro) versions, and the pro versions are at a reasonable price.
https://play.google.com/store/apps/details?id=com.goseet.VidTrim
This one "VidTrim", but not OpenSource: https://play.google.com/store/apps/details?id=com.goseet.VidTrim
However, there is a paid adfree version, too.
If I remember correctly Vid Trim can do it: https://play.google.com/store/apps/details?id=com.goseet.VidTrim
You can't select the frame exactly of course
I'm not aware of any video editor native to the A7, but I use VidTrim.
This app description says you can merge videos.
https://play.google.com/store/apps/details?id=com.goseet.VidTrim
Download the app VidTrim! It has a frame grabber built in. :) https://play.google.com/store/apps/details?id=com.goseet.VidTrim
There is also a paid version with no ads so give the free one a try and see if it suits your needs.