Agati is Sesbania grandiflora
It's also known in Sri Lanka as 'katuramurunga' where the flowers and leaves are eaten see my post (#25) for (Katuramurunga) Mallum in the 'What to do with turmeric' thread.
Ive also seen it in Indonesia (known there as Turi) and Thailand (Dok khae)
there is a red- flowered form (species?) that is used in the same way.
Mahwa is a member of the Sapotaceae family (so many useful species around the world) and a very important honey source in India.
I was looking for seeds of this species about 20 yrs ago and there where a few plants being grown in WA. but I dont know if they're still growing.
It is a tree worthy of growing in Aust.
Bringing seeds into Aust. IS perfectly legal , just make sure they're clean and clearly labelled and declare them on arrival.
some seeds are prohibited, some restricted (you need a permit) and many are permitted.
Best idea is to go to the AQIS website and find out what is and isn't permitted.
For expediency, it's also a good idea to email AQIS before you depart, to alert them of your arrival and flight no. so that they know what to expect.
I've found them to be usually very helpful if you're up front about it.