Mermail Abyssturge

If i use Mermail Abyssturge's effect, can i return to my hand the same monster i discarded for cost ?

Yep, you can.

I think it works like lumina, zombie master, and etc. We have a dispute about that rulings here, in the occurrence that I discard an atlantean marksman or heavy infantry and I choose that card to return to my hand they say the effect of the atlantean has missed the timing or has not fulfilled the condition. ?_? I got tired of their complaints so I went back to hero beat and beat the sorry losers again.

you can target the monster used for the discard if you already have something to target in your grave before you activate the effect.

yeah they agree with that part, what they don't agree with is when for instance I discard Altantean Heavy Infantry with Abyssturge's effect, they say I can't activate the effect of Atlantean Heavy Infantry bcoz it wasn't confirmed to be in the grave??

they are probably trying to compare it to the xx-saber darksoul ruling. it doesn't have to remain in the grave for the card to resolve, it just has to be discarded. so in your example you should be able to use heavy infantry's effect after Abyssturge's effect is finished resolving.