First of all, the concept of "100%" is very vague. From the chemical definition, no toilet water (this word needs to be clarified) is not an aqueous solution, and there is no concept of 100%. If you mean "pure plant extract" and "high concentration", you can use the word "saturated" flower dew.
Besides, flower dew, if you mean the plant extract obtained by distillation, then the water-soluble part can generally be called pure dew and flower water, but the term refined dew is more recommended. Components that are insoluble in water are called essential oils.
About self-made, according to the scale, it can be divided into laboratory preparations and industrial preparations. The two methods are completely different in equipment and operating procedures. Here, let's briefly talk about laboratory preparation. In fact, anyone who has done inorganic chemistry experiment, organic chemistry experiment or biochemical experiment should know that this preparation equipment is very simple. You need distillation equipment (distillation bottle, kerosene lamp, sealing plug, air pressure regulator), condensation equipment (condensation tube), collection equipment (trumpet, triangle bottle), separation equipment (separation funnel and the like), storage equipment (dark essential oil bottle) and so on. Equipment construction drawings are also easy to find and can be found in any laboratory operation manual. A key to distillation is water, preferably distilled water or deionized water. Water does not contain any impurities, which is more conducive to purifying flower water.
However, it is difficult to prepare essence in the laboratory. Because the output is extremely low, if you intend to distill enough, you need to circulate it many times, and if possible, you need to carry out secondary distillation and tertiary distillation. If it weren't for scientific research, it wouldn't be worth investing so much manpower and energy.
The second and third questions are really too big. There are hundreds of kinds of flowers that can be used to prepare essence dew, and each essence dew has different effects on human body, so there is no most favorable one. This statement is too subjective. In fact, different people have different opinions. I have some information about Essence Dew in my space, so you can refer to it.
As for the yield, it also varies from flower to flower. For example, pure essential oils, which distills less than 1 kg, needs 3-6 rosewood cores, namely 18 tons of sawdust. As for the distillation of flowers, the proportion is even lower. Moreover, in industrial preparation, the proportion of water and flowers is a technical problem, and the proportion of different wineries is different, and it is absolutely the technical secret of the merchants and will not be easily told to outsiders. In fact, you can infer the purity of those flower water on the market.
This field is extensive and profound, and I can only briefly talk about it, hoping to help you.