It should be a clipping mask. Holding 'alt' and clicking on the bottom border of the layer should remove the mask. Or simply right click and search for something called 'clipping mask', 'remove clipping mask',...
If my answer is not engough: Adobe Photoshop - Clipping masks
I'm sorry for your loss. I've done this exact project with an image of my cousin and am most familiar with Photoshop, though other programs exist (GIMP comes to mind). Given that Adobe now offers a 1 month license through their Creative Cloud for $10 (Photography Edition for Individuals) - it's not that bad a cost to use, even if just for this one project.
How to make sure that photos edited in Photoshop CS6 don't look different (more saturated) on phones
Don't look at them on most phones. The screens on most phones are too bright, too saturated, and too blue (calibrated to around 7000K).
If the devices you are checking on are not colour-profiled then there is not a lot you can do. Any image is going to look different on each.
The best you can do is ensure that it leaves your machine in the best possible way.
This assumes your monitor is already calibrated & the profile is available to your OS.
Make sure Photoshop is set to the ...
Normally you would include a an object known to be white in each frame. There are special things for this, most commonly White-Balance Cards Then, you use the software to pick the WB from that point. Repeat for each image and the colors will now be the same.
For levels, I suspect you mean that you got a different exposure. To fix that, you must shoot all ...
When you go do Display Settings and select 100% for Scaling of Text, Apps and other elements it should work. I tried at various resolutions and it always gave me your error when selecting anything larger than 100%.
It even worked at my highest resolution setting at 3840x2160 as long as the scaling was 100% (which of course makes the program unusable since ...
Expecting a piece of software discontinued in 2013 to work with an operating system released in 2015 is a bit unrealistic.
You need to either:
Use an OS for which your software was compatible
Update your software to a version that works with Windows 10
Photoshop CS6 runs fine on Yosemite, no issues with it that I've encountered, though I don't use it as much since I have CC. It's there as insurance. Your hardware isn't going affect this.
I would suggest looking at the CC 2015 update, though, because there are some really very useful speed improvements that can take advantage of the newer hardware much ...