Board Game Arena

Sevens is one of my favorite card game. However, the Fan Tan that I usually play is that if you are not able to put a card on table, you need to "Donate" Or face down one card instead of passing (According to 1990 4 Card Game - Fan Tan) But maybe I play Fan Tan with the wrong rule all the time. Further, starting player is the one who have 7 spades instead of any sevens. The winner is decided by having the lowest face down card when you pass.

There are tons of variants in public domain games.
'Burning' or 'discarding' variants you mentioned were considered while developing the game.
However, they were ultimately dropped because they severely hindered the game flow by removing 7 or center cards:
https://boardgamearena.com/bug?id=72207

7s can't be removed because of the "if you have a playable card you have to play it" rule.
I am also most familiar with this exact version (we play it when we get together for Lunar New Year), so I was surprised it was rejected.