Does the Champion’s Tablet sums offerings from all characters

The boat changes the sex/gender of your character. If you enter it as male, you come out as female and vice versa. It doesn't change anything else about your character, so any hair/makeup/tattoos/body style/etc remain as before.

Since so much of your body shape is obscured by armor, the change isn't very obvious. Additionally, there are absolutely no known gameplay differences between playing as male vs. female, in the base game. If you have the DLCs though, there are certain armor sets that will give you hidden benefits if you're a certain gender.

I'm a blue knight and yes I have to wear my ring for you to summon me and you must be in human form with your ring on to summon me. I've been summon from random places all across the map, even to areas I hadn't yet been too. The only place I wasn't summon to was the bell tower as that was a pvp area for the protectors of the bell covenant. If you were in that area, if you weren't human, if you weren't wearing the ring and one of us wasn't wearing our ring, that is why you couldn't summon one of us.

As for summoning and invasion The way it worked in dark souls 1 and dark souls 2 are different to make it more fair. It depends both on soul level and soul memory. Your soul level is what level you are while your soul memory is based off of how souls you spent on your armor weapon and levels. You can find it in your player status menu. It's to help fight against over powered people fighting under powered people.

Hope this helps and praise the sun.