Macbook air 2015 Final cut pro

As Ian said, it will work, but it not the best choice for video. The integrated GPU is not very powerful, and it will use part of the existing RAM. The i5 processor is only dual core with no hyperthreading. 8GB (minus the RAM allocated to the GPU) will do but having 16GB will give your mac some breathing room.

If you can get a slightly older (say 2013 or 2014) 15” MBP with a discrete GPU you will be much better served.

You probably can but you can find out for certain by downloading the FREE 90 Day Trial.

https://www.apple.com/uk/final-cut-pro/trial/

It is completely free and won't cost you a penny.

At the end of 90 days it will just stop working unless you decide to buy it.

You can surely edit 1080p material in that mac.