So i was thinking if i send a bitcoin transaction without the miner fee or a very low fee what will happen ? would i get the coins back eventually ? or they will just stuck there forever ! and if that happened how to do that double spend ?
First of all, I wouldn't suggest that you do that because it is a very stupid idea.
If a transaction goes unconfirmed for too long, it will eventually disappear from the network. Most clients will remove it from their pool of unconfirmed transactions at some point. And yes, the money should return to your account. When most clients have removed it, you can go ahead and send the transaction again, if you wish and I would suggest to use a higher fee. There's not a precise time when the transaction will disappear from the network, it could be days or up to a week. This is why it's always recommended to set a transaction fee.
Yes.Don't try that especially in this period where there is huge number of transactions stuck.If you still send it without a fee or with a very low fee,then it may take even one or two weeks to get confirmed or else,it may return to your account.I had that experience when i forgot to set transaction fee manually in my electrum wallet and it took around two weeks to get confirmed.