No player votes until the spell or ability resolves. Any responses to that spell or ability must be made without knowing the outcome of the vote.

You must vote for one of the available options. You can't abstain.

Because the votes are cast in turn order, each player will know the votes of players who voted beforehand.

If Custodi Squire is not on the battlefield when its ability resolves, the vote will still take place and the card(s) that had the most votes will still be returned to your hand.

The phrase "the vote is tied" refers only to when there is more than one choice that received the most votes. For example, if a 5-player vote from among three different choices ends 3 votes to 1 vote to 1 vote, the vote isn't tied.

Players can't do anything after they finish voting but before the spell or ability that included the vote finishes resolving.

If a choice has no votes, it can't have the most votes. If all choices have zero votes, the voting ability has no effect.