When using both the perfect aspect and also the progressive aspect for my verb “to have been studying”, should I use the present tense has or the past tense had here?
Your use of 'moved' gives the sentence past tense so it should be 'had'.
The Past Perfect expresses the idea that something occurred before another action in the past. It can also show that something happened before a specific time in the past.
She had been studying there for 8 years then she moved to another school. That is technically correct.
The second of the two, for the reasons already given. You could say "she has studied...and will be moving...". The second sentence is more an indicator of the past. You could say "She has been studying there for six years and still is studying there". You wouldn't use "had" in that sentence, because "had" signals cessation of the thing that the person "had" been doing. Or you could simply say "She studied..."
