My first question is what is seed/password? I can write anything and come in. Does it mean that if I write someone else seed I will get access to his IOTAS? If I log in with a short seed like "test" and people send IOTAs to it, will my IOTAs be accessible to all people that log in with "test" seed? Is an "account" in IOTAs only a long "seed" string of characters that is very unlikely to be repeated? So to get an "account" I just invent a random long string and use it as a seed?
Question 2. I following message: Add more nodes you only have 1. Try to add at least 7. What should I do about it?
1. Yes, it's called a brainwallet. Cryptography and probability ensure that when using 81 random characters, the entire population can continue to use unique seeds indefinitely with the same seed being used practically impossible. Think of the same person trying to win the lotto first division 100 times in a row. It's practically impossible.