x put a 3 of hearts in combination ace, 2, joker and 4 of hearts and get the joker. now x has 1 card left and he isn't allow to junk that card, how he can continue?

IF he has only one card in his hand, he isn't supposed to take the joker, since he knows that he won't be able to play it anyway; as simple as that.

yes but sometimes persons do that in mistake so what he can do on that time. my question is this. how the game will continue?

Junk the joker and lose 300 points.

but we arn't allow to junk!!!

Can you reproduce this? I didn't play rummy in some time, but i believe that in your case, you would actually finish the round before even getting a joker, but i can be wrong on this.

you imagine that position, x meld a new combination: 1 2 joker and 4 of hearts. now i i draw a card and it's 5 of hearts. first i extend ace 2 joker 4 of hearts with 5 of hearts then with 3 and get to joker by mistake of cource there is better positions about that and yesterday i tested the better position but i can't remember that good one however it's a right example. now my question is it, after this fortuity how the game will continue because i'm not allowed to junk my joker and get 300 penality points

Well you can't play rummy like that and not think about jokers and just say people can do it by mistake. In case game really doesn't continue then yes, in that case playroom should probably allow you to junk it but there's simply no reason to do something like that.

if people can't play like that so here room must don't allow to people for taking such cards then we forcethinking about junk. we should To consider all aspects

We also need to use our brains when playing, i do agree that playroom should disallow this but you need to send a history so we can see how did it work.

you can test it, i can say this work with extending 1 combination that contains joker with your last card and get it. just all is it. i know what all you say about brain and others, however it's a serious problem and must fix