Front cameras mirror what they capture, which is why selfies often look subtly wrong and any writing in them appears backwards.
Front facing cameras show you a mirror image so that moving left on screen matches moving left in reality. Some phones save that mirrored version and some flip it back, which is why a shirt logo or a sign behind you sometimes reads backwards in the saved file.
Flipping horizontally is lossless. The same pixels are written in the opposite order, so nothing is re-compressed and the image is exactly as sharp as it was.
Flipping is not the same as rotating. A flip mirrors the image, a rotation turns it. If a photo is on its side you want rotation, not a flip, and flipping it will only make the text backwards as well as sideways.
No. It rearranges existing pixels without re-encoding them.
No, rotate it. Flipping mirrors the image and will leave any text reversed.
No.