Hey, no problem, just thought these answers might benefit others here as well. I'll try to give you some concise responses and point you to some additional reading material for reference also.
1. With POTS symptoms tend to worsen in upright posture and alleviate while lying down (supine). Other stimuli can worsen symptoms such as exertion/exercise, heat, eating a large meal, caffeine or other stimulants, stress, dehydration, and hormonal cycles. As such, symptoms will tend to come and go, though people with severe cases of POTS (often with significant autonomic involvement) may have some chronic symptoms that worsen or improve but may not entirely alleviate (or may only alleviate with medication).
2. I'm not sure where you got that, but 30 minutes is irrelevant to a diagnosis of POTS. In POTS the heart rate goes up (and is sustained at) at least 30 beats per minute when you go from lying down to standing up/head up tilt within 10 minutes of being upright and symptoms of orthostatic intolerance are present (lightheadedness, nausea, palpitations, shortness of breath, etc.). This resolves when you lie down again. See the additional reading material I link below for a detailed discussion of the mechanism of this disorder.
3. An EKG with a normal procedure (while the patient is lying down, resting) will likely be completely normal in a POTS patient with no other disease process. An EKG done during a tilt test (while the patient is being tilted upright specifically to test for dysautonomia such as POTS) would most likely show sinus tachycardia. Non-sinus rhythms would likely indicate a diagnosis besides POTS. (Some POTS patients have heart rhythm abnormalities in addition to a POTS diagnosis, but this would be two separate things.)
http://www.medhelp.org/health_pages/Neurological-Disorders/Further-Reading-on-Dysautonomia/show/696?cid=196
I recommend the first and second links on our Further Reading page to you especially; keep in mind that this list includes many links to articles about other types of dysautonomia that won't be relevant to POTS per se, but feel free to look around.
http://www.medhelp.org/health_pages/Neurological-Disorders/Diagnosing-Dysautonomia/show/827?cid=196