Are they physically forced to vote for Putin? And how widespread is the electoral fraud?

Well, some decades ago if you were a school teacher, you were _asked_ to (1) vote "right" yourself (2) call all parents and ask them to vote "right". If you disobeyed, the school got problems and you got problems. Maybe not enough to make all people comply, but sufficient to get the right outcomes. Same goes for all government-funded workers.

Since then I think they simplified the system and just forge the results outright.

This is informative https://politics.stackexchange.com/a/27658/25206

tl;dr Other parties are Putin-like, and if/when a genuine alternative emerges, Putin deals with them ruthlessly. Example: Navalny was the charismatic leader of a small but popular rival party with anti-corruption policies. He was initially delegitimised (not allowed to partake in the 2018 elections due to [likely fake] charges of embezzlement), then poisoned (nearly died), then imprisoned, and then killed while in prison.

Consider the terrifying message that sends to would-be political rivals...