1. Yes, it's Past tense from 'ходить' и 'идти'.
singular m.шёл (he went) f.шла, n. шло, plural шли.
Past Participle шедший, шедшая, шедшее, etc.
2. Note that neutral gender in Past in Russian is used sometimes 'impersonally', for 'abstract' or generalized situations. Thus:
- Before giving numbers - Родилось два ребенка. Пришло пять человек. Родились два ребенка. Пришли пять человек. Both are possible.
In the first ones you are more concerned with counting things and giving numbers. "Пришло пять человек" - when you are talking about the whole number of people who came to a party or a conference etc. during an evening. You may thing of using neutral here as if there is 'в общей сложности' (in sum) or 'всего' in your phrase, but you've omitted it.
If they came together as a company and you're describing the very moment they came, meaning e.g. "a group of 5 people has come right now" - you'd rather chose 'пришли'.
Пришли 5 челвоек is used when you're concerned with the people themselves, or with telling the story or describing what you've seen etc.
The same fro children: saying 'родились' you're more concerned with the children then with the number.
- мне пришло в голову, что ....It came to my mind that...
Here supposed subject is это (it/that). Это никогда не приходило мне в голову...
In this sense это is genderless.
- of course, родилось is used before any neutral noun. Дитя, понимание etc..