You said "The people who are martyred during the tribulation who refuse the mark of the beast will be beheaded. And some people have seen that the devil and his "aliens" who enforce the mark will get a "kick" out of putting the mark into the decapitated body after the death."
Your first statement comes from scripture, but the second one comes from a source other than scripture that you are assuming has the same validity.
It makes no sense for satan or his followers to put the mark on a dead, beheaded body, in fact it would send a message counter to satan's tribulation message. he is telling people take the mark and live, and then he makes it look like he kills some who took the mark. I don't think so. (although even if he did it would mean NOTHING)
The "some" you are referring to are making statements inconsistent with scripture. Does not God warn us to filter everything through scripture?
And what a blessing for Him to give us such a valuable tool. What a loving God who doesn't want us to be ... confused.