Does PNG/APNG support 60 FPS animations, or are they limited like GIFs? [closed]

Yes, APNG supports 60 fps

The APNG Specification says:

fcTL: The Frame Control Chunk
The delay_num and delay_den parameters together specify a fraction indicating the time to display the current frame, in seconds. If the denominator is 0, it is to be treated as if it were 100 (that is, delay_num then specifies 1/100ths of a second). If the the value of the numerator is 0 the decoder should render the next frame as quickly as possible, though viewers may impose a reasonable lower bound.

So technically APNG can be as fast as the decoder can decode it. Although there may be limits set by various encoder/muxer & decoder/demuxer implementations.

Try it

You can try it yourself by using the testsrc2 filter to generate a sample APNG file:

ffmpeg -f lavfi -i testsrc2=d=1:r=60 -plays 0 output.apng

For more info for the APNG muxer see ffmpeg -h muxer=apng.

Was APNG expanded from the PNG extension?

Yes. From the specification:

APNG is an extension of the PNG format, adding support for animated images. It is intended to be a replacement for simple animated images that have traditionally used the GIF format, while adding support for 24-bit images and 8-bit transparency. APNG is a simpler alternative to MNG, providing a spec suitable for the most common usage of animated images on the Internet.

APNG is backwards-compatible with PNG; any PNG decoder should be able to ignore the APNG-specific chunks and display a single image.

APNG is older than PNG, right?

PNG came first and is older than APNG.