If you go in the kanji dictionary, beside each reading it has a symbol that will give you an idea of how often the reading is used
"These symbols denote when this reading is typically learned in a Japanese school. 小: Primary school 中: Middle School 高: High School x (or nothing): unknown, or not taught in the above school levels"
If it is taught in primary school, it is probably used a lot in every day life.
If it is not taught at all from primary to high school, it's probably not that common.
For the kunyomi readings, you only need to know the part before the ., i.e. in this case the わ
The part after the . would be written in hiragana (and isn't part of the reading of the kanji)
Yes about it I knew it, but are they used in real life ? the different conjugations.