Apparently, all versions of the Federation Charter seen in-canon and in various semi-canon texts strongly imply that technology sharing takes place as soon as a planet becomes a member of the Federation. Has any planet resigned membership from the Federation after this technology transfer occurred? The Federation seem pretty thorough in their application process (several planets have been denied) but has any planet ever 'scammed' the Federation to get advanced tech by joining and then left after the transfer?
In canon, no planet has ever scammed the UFP in that way because, as you pointed out, the application process is very thorough and lengthy. The UFP can spend years or decades thoroughly reviewing a planet's application for membership to ensure that the application is honest and that the planet does conform to the guiding principles of the UFP's Constitution.
The only known canon example of a planet who willingly broke off from the UFP is Turkana IV, an Earth colony and place of birth of the late Lieutenant Natasha Yar. As far as we can infer, it had nothing to do with having gained technology from the UFP.
For reasons that were never stated on screen, the planet began to experience unrest in the 2330's. The government was apparently unable to do anything to remedy the situation and finally handed much of the power to the two major factions at the time, the Alliance and the Coalition, as its final act before it broke down completely. The planet severed its ties with the Federation in 2352 and was still in a state of civil war when the Enterprise visited in 2367. Its status afterwards is unknown.