Answered question
I subscribed/selected Mobil Plan and ordered SIM card on April 11, 2019.
I received my card and activated it on April 14, 2019.
When I was subscribed: before April 12, 2019 or after April 12, 2019?
What monthly price I'll have after stabilization period: Launch Price or Regular price?
You subscribed after April 12. It when you activated your account that matters, not when you ordered the SIM.
Other answers
Unfortunately you activated on April 14. Unless Fizz does other changes, you will fall into regular pricing after the stabilization period.
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