So to sum up, if what I get from all this is correct,
1. Only skills with borders are able to evolve, with (number of borders - 1) being the amount of times it is able to evovle.
2. The only way to know if a skill on a weapon is able to evolve is to check it out for extra borders at momo.
3. All skills on all weapons are extractable, being limited only by momo's friendship level and the extracted skill has to be at max level before extraction is possible. Skill level on the particular weapon is reset after extraction.
4. Skills cards obtained are single use per extraction and when applied to another weapon (limited only by weapon type - odachi skills can only be applied to odachis) replaces a skill at random.
5. Target for skill replacement is currently equipped weapon.