FAR 91.215 (b)(3)(ii) -- transponders-- does the "or below 10,000' MSL" clause have any practical significance?
The answers to the questions appear to be &quot;yes&quot;, &quot;yes&quot;, and &quot;no&quot;.  Neither FAR 91.215(b)(2) nor FAR 91.215(b)(4) have any effect above 10,000' MSL.
The &quot;or below 10,000' MSL&quot; clause in 91.215(b)(3)(ii) has no effect on anything at all and does not prevent an aircraft with no electrical system from operating above Class B or Class C airspace as long as it is above 10,000' MSL.
This is clarified in this 2006 interpretation from the FAA Office of the Chief Counsel.
It possible that the original intent of FAR 91.215 was to prohibit aircraft without electrical systems and transponders from flying above 10,000 MSL above any Class B or C airspace that lies within a Mode C veil; if so the regulations were inadvertently written in a way that did not accomplish this.  This has been rectified in FAR 91.225, pertaining to where aircraft without electrical systems and without ADS-B-out will be able to fly starting January 1, 2020-- these aircraft will no longer be able to overfly ANY Class B or C airspace, regardless of altitude and regardless of whether or not the airspace lies in a mode C veil -- see related question What additional airspace will be off-limits to an a/c w/ no elect. system or xponder under 91.225 (ADS-B) compared to under 91.215?