به سلامتی و میمنت

While it uses words common in religious contexts, it is considered a cultural/formal phrase rather than a strictly religious one. People of all backgrounds use it.

Yes, it is excellent for formal emails, especially when congratulating a client or a professor.

'Mobaraki' is more common and slightly less formal. 'Be salamati o meymanat' is the 'premium' version.

It's a bit too heavy for a child. For a child's new toy, just say 'Mobarak bashe'.

Rarely in modern speech. It almost always appears in this fixed phrase or in 'به میمنت و مبارکی'.

Yes, the order is almost always 'Salāmati' then 'Meymanat'. Changing it sounds unnatural.

In Dari (Afghanistan), 'Ba salāmati' is common, but 'Meymanat' is less frequent in daily speech compared to Iran.

It's possible if it's a milestone birthday (like 50 or 80), but 'Tavalodet Mobarak' is the standard.

Absolutely! It shows a very high level of cultural integration and usually earns a lot of praise from native speakers.

It literally means 'auspiciousness' or 'blessedness', coming from the root for the 'right side'.