Quote from: pooya87 on December 29, 2017, 05:04:51 AM

it actually depends on your wallet settings!
i am not sure if Electrum new version added a "spend unconfirmed transactions" or not and i have never checked it otherwise either. but my guess is that it will spend them.

It sure does have that setting... and has had for a while (it was also in the v2.x versions, not sure when first added):

by default, I believe this setting is switched OFF.

Quote from: Psybetronic on December 29, 2017, 03:41:06 AM

Also if I transfer from a different online wallet (coinspot) to the same receiver address using the highest miner fee, will the receiver still get the second transaction.

You can do what you want from a different wallet... it will have no effect whatsoever on any transaction to the same receiver address from a different wallet.