This is a bra with shaped cups, side fastening and a halterneck style construction for the straps, which are anchored in the centre of the back. The construction does provide support, but like all soft bras, not as much as an underwired construction. The fastening can be by tie or by a fastening such as velcro.
This design does not give directions for different sizes: it gives general directions on construction, with suggestions and tips on measurements, stretch, etc. I suggest you use a comfortable conventional bra as a model. As you need to tailor it to your size as you go along, I would suggest that it is only suitable for those who are reasonably experienced in crochet and are comfortable with making it up as you go.
The fastening can be on one side or two, so if you’re pregnant or nursing, the adjustable nature of the bra can help deal with the inevitable changes in your size.
The instructions are written (no chart) in UK terminology, but with a translation into American. Four photos in the pattern show the main points of construction.