@Tangelo777 Here are the answers to your questions:
(Note that, for every question also counts: "keep the number reasonable. No more than 3")
> What happens if two accounts that belong to the same player, play in the same tournament and get automatically paired? Does one of them have to constantly avoid moving to prevent breaking your rules?
Having two accounts in the same tournament is rule-breaking.
> Is it ok to use many accounts at the same time against a single host at a simul?
No rating is involved so I'd say it is allowed, however it would be fair if you tell the host.
> Is it ok to bring multiple accounts to the list of top players and control more trophies?
Only one account in Top 10 allowed. In top 50/100, two accounts is not really a problem.
> Is it ok to use several accounts to vote several times at surveys and polls?
Surveys and polls?
> Is it ok to use several accounts to comment on each other's forum posts?
No. I can see this happen in feature requests where people are discussing whether something is a good idea or not. We wouldn't want the opinion of one person to be spread over multiple accounts.
> Is it ok for multiple accounts belonging to same person to follow each other and generate massive lists of followers?
Followers are useless, so this is no problem. But "massive" lists shouldn't happen, see the general note at the top.
> Is it ok to use multiple accounts to play different variants on different accounts and spread out trophies?
That's fine.
> Is it ok to use many accounts to play rated games against random people? It's needed because simuls are casual and never rated.
If "many" <= 3 (see general note).
> Is it ok to use many accounts to join teams and make them very popular?
No reason not to: having two/three accounts in your team won't make it more popular. Team size doesn't matter anyway. However, joining the team should not be the only purpose of your second account.
> I want to add that
@Lance5500 is an official coach. He may need multiple accounts to review himself and other coaches. He may also pose as several different coaches competing among themselves.
@ProgramFOX do lichess rules permit that?
That's not allowed.