So I played in a mini tournament and during the super fun games some weird question occurred.

Round 1 vs TES: 2-0
Game 1 he opened with gemstonemine into ponder. I played taiga, exploration, wasteland. Next turn wastelock then early combo!
Game 2 he couldn't play through 2 spheres and again early token!
TES has a horrible manabase!

Round 2 Belcher 2-0
Game 1 he mulled to 5 played landgrant and revealed only fast-mana, I go for an early token and connect.
Game 2 I sided out the mazes and the pfires. He played a turn 1 belcher but was 1 mana short to activate. I played taiga. Next turn he draw tinderwall and activated belcher. I respond with crop rotation on chasm. Eventually I got a chasmlock.

So I had multiple stages out (one on chasm). What exactly happens if I stage the stage(that is chasm)?

Ok the game goes on for a while and I played some spheres and stuff but I couldn't find a Ddephts. Eventually I found it but than I realised, if I want to attack with my token, I had to get rid of my chasm and he can belcher me. I had about 30 cards in my library milled my lone pithing needle and sided out all Pfires :(

Is it considered stalling if I know I cant win this game and continue to play to survive as long as possible?

Since I didn't care I just go for it and waste my chasm and attacked. He didn't belcher me. After the match I asked him why, he said he is new to legacy and didn't know what's going on the whole time...

Round 3 vs infect: 1-2
Game 1: Turn 1 token gg.
Game 2 and 3: I had all the answers but a very well timed FoW from my opponent always pushed through the last infecter!