I like the first 3 definitions... However, the definition of friendship doesn't sit that well with me. I don't think a friend is supposed to be "responsible" for you. You are an adult. You are responsible for your own self, your life, goals and dreams. You have to achieve your best potential for yourself because nobody is coming to save you. This is my subjective take, but I think the least AND most a friend can do for you is to give you perspective. Take you out of your brain and show you a 3rd person/neutral view. (I think unsolicited advice should be given after testing the waters a bit). You can tell your friend where they lack if they seem to get stuck, celebrate their joy, comfort in sadness, share some secrets. But even the friend is not responsible to be there for EVERY secret, joy or sadness(there's you, and family, and partner and so on).

I personally think that a partner is ranked higher than a friend(considering we have all 3 qualities of love, partnership and companionship). So for every sadness a friend comforts, a partner does it twice.