Order of Wizards

When the Istari were sent as emissaries, were their powers as Maiar locked when they took the physical form of old men or could they still access it but wouldn't do so because they were forbidden?

Does Gandalf (or the other Istari) remember their earlier life as Mair before coming to Middle Earth?

So when the Valar sent the Istari east to Middle Earth, the two blue wizards, Alatar and Pallando, are believed to have gone East in an attempt to thwart Sauron’s influence in those regions. However Tolkien implied that they failed, and ended up starting cults.

So in the Fourth Age, with Sauron gone, is it possible that one or both of them could become the new Dark Lord(s)? I don’t think they immediately could have risen to power, especially as long as Aragorn and most of the other Fellowship members were still alive, but perhaps during the reign of one of Elessar’s descendants?

What are your thoughts?

Does anyone know the reason for the Valar imposing the restrictions they did on the Wizards?

We know the Valar were reluctant to openly war against Morgoth until being convinced to in the War of Wrath. They wanted to avoid the massive damage to M.E. which did occur. However, Sauron was less powerful than his master, and his destruction would could massive damage to the lands his power was imbued in.

Why would the Wizards be restricted from using their full power and fighting Sauron as peers? Together they should have been able to severely hinder him, if not defeat him. Even if using their true power and revealing their identities, they could still guide the free peoples of M.E. without dominating them. In fact, openly coming as emissaries of the Valar might have made the free peoples more likely to listen to them and stand against Sauron.

So Gandalf talks about Saruman being the greatest of the wizards in the 1st Hobbit. Why was he the greatest though? Was he just more powerful?

Are all of the wizards in Middle Earth Maiar or are just Gandalf, Saruman and Radghast Maiar. Please help. My brother says they all are but I don't trust him... And correct me if I'm wrong but isn't Sauron a Maia? So how come he isn't a good guy? As much as I love Tolkien and his lore it confuses me too much...