Only once after every 5 lvl.

There is CN answers. But there is too many of them. So it's better to create your own data base))

You can invite 1 on each day (3 if you have Jonin Medal). He will come in next day. Otheres will be random.

All versions of that character get bonus, that's why there is only one form of each character in Home.

As far as i know - it's not. But you probably can get those frags from mission, wich you can get by up bond lvl by 5-10-15. Again - i'm also not sure)

Specially for you i attached a second table))

When you level up ninja (in your case it's sakura) you raise stats ONLY for all form of that ninja. In your case it's all forms of Sakura. But when you level up any ninja you also level up your Bond Level, wich raise stats for all ninjas in current formation, but one level up gives only a little bit. For example o first screen you can see my Sakura Level. Those bonuses get only sakura. On second screen you can see my bond level. Those stats get all my ninjas in current formation. I hope you understand me)

By update.

Otheres not added in game yet.

Up!

They don't add in game yet. Will be in future updates.

Up!

Update the table.

Sadly - but i don't have data on them yet. Also Hashirama is not presented on CN, so i probably just can't have data about him)))

Okie, i update it.

Added latest characters from CN. Has to divide the table into two parts - too many characters)

Yes, Madara. Some ninjas (like 10) are only on Cn right now, but will be here eventually, so i add them here))

It is accurate. But about other ninjas - they do not added yet in here. But even after that, you need to get them, so you can talk with them at home.