Majesty's Fiend vs Michion the Timelord
Q1: Yes, Michion can be Normal Summoned from hand.

This is not an activated effect, but a condition on the card itself that grants a summoning procedure. Therefore, Majesty Fiend's effect does not prevent it.

Q2: No to all three.

Michion's effects which prevent his own destruction and prevent damage from battle are not activated effects, but continuous effects. Therefore, Majesty's Fiend does not prevent their application. The effect of halving the opponent's LP, however, is an activated effect (you can tell by the presence of the colon); it will not be activated at the end of the battle phase due to Majesty's Fiend.

Q3: No, Michion will remain on the field.

Michion's effect to shuffle itself back into the deck during the standby phase is an activated effect (again, note the colon), and therefore is prevented by Majesty's Fiend.